Londo and G'kar are not minor characters, though important, next to the stations crew, but are actually the two main protagonists. All the other characters are really just supporting cast to help telling their very own story.
Also, Londo isn't just an alcoholic. He is also addicted to power and prestige. In his constant effort to gain more respect he allies himself with other power hungry men, never notices how much damage they are doing to others, and when he realizes what he has done, he can never turn his back on his allies because he can't cope with loosing their respect. He lies to what few friends he has left, to hide his association with other conspirators, and when openly accused becomes violently angry and makes up justifications for what he did. And every time he manages to break free, it takes only a tiny nudge by a former ally or a personal tragedy to forget about all his promises to himself to never get drawn into it again. Mr. Morden also uses the classic drug dealer tactic of offering some first tastes of great power for free, but later makes increasingly greater demands for his continued service as Londos ace in the hole.
Word of God on several occasions has it that the entire main arc is essentially Londo's story. Londo even gets the very first spoken lines in the entire canon, the opening narration of "The Gathering":
Londo: "I was there at the dawning of the third age of mankind..."
Pretty much the entire first episode, Midnight on the Firing Line. All of it.
President Clark's entire administration has some very chilling real life echoes in at least two, if not three, different American Presidential periods - and one of them didn't even start until the 2000's rolled around (i.e. after the show's run had ended). Pure brilliance on Straczynski's part.
The Vorlon method of teaching the younger races doesn't work and never would! Just look at the Minbari, the only race we know to have significant long term influence by the Vorlons, they seem to have barely progressed technologically in the thousand years since the last Shadow war. The Vorlon teachings make a society so disciplined and rigid that there's little room for creative thought which leads to few innovations and improvements. Sure, to a Vorlon taking a few thousand years to progress is not a concern, but their immortal, the younger races can't do that because they don't live long enough to benefit from that kind of lifestyle. You'll notice that every single advancement we know of from the minbari occured due to direct alien influence (Valen restructured Minbari society and made all the castes equal, the Vorlons allowed the Minbari to use some of their technology to creat the White Stars and everything that happens to them during the series happens due to Delenn's constant contact with humans). Notice how humanity managed to come up with ships that can fight and destroy White Stars in a little over a decade after being completely ineffective against the Minbari during their war? And all they had to work with was one Shadow ship for a couple of years, while the Minbari had Vorlon access for centuries and still needed the Vorlons to directly give them the technology. While the Shadows' methods go too far as well their methods actually do get results it's just they go too far and get themselves destroyed.
Which is the whole point of finding a "balance between order and chaos", as Delenn had said in "Into the Fire". "Who are you" and "what do you want" are both fundamentally important questions for all sentient beings, defining where you stand and where you are going, respectively. Focusing on just one without the other each carry its own set of dysfunctions. As an old saying goes: "give your children both roots, and wings."
Why is "ahel" ("Ah, hell!") Minbari for "continuous fire"? It's something Valen/Sinclair said once when he was backed into a corner and forced to shoot his way out.
The Shadows believed that they would die if anything Vorlon touched Z'ha'dum. Most assumed it's the White Star that did it. However, something Vorlon touched the planet before then: Sheriden was carrying the piece of Kosh with him. The Shadows sealed their own fates by bringing him there.
Everyone we see answer Morden's question ("What do you want?") gets what he asked for; Londo gets a return to Centauri Empire's imperialist days, and later G'kar gets to see the Centauri Empire bombed to rubble, and in between, Vir gets to wiggle his fingers at Morden's head on a spike. Of them, though, Vir was the only one who asked for something which, by the time the request was fulfilled, he actually wanted.
There's also a theory that Morden reacted so badly to Vir's answer because he knew that, one way or another, the Shadows saw to it that everyone who answered that question got what they asked for.
Morden visiting Lennier on the Day of the Dead seems fairly random, a surprise for the sake of a surprise, until I realised it makes perfect sense given Lennier's character arc for the season, Morden was the representative of the Shadows who always asked "What do you want?" and Lennier is now blinded completely by what he wants, Delenn. Just as Morden led those who answered his question into tragedy (except Vir, who actually got what he wanted), so too will Lennier's pursuit of what he wants.
In The Gathering, the Fake!Lyta attacks Dr Kyle using what will later be shown to be a common Minbari pike fighting move, hinting at the assassin's true identity.
In War Without End, after they are informed of the special devices to protect them during time travel, Ivanova mentions the pilot who died of old age after being exposed to the time rift, then looks at Sinclair, significantly aged since his last appearance, and declares that he must have been lucky during his own visit. That could also be the reason for Garibaldi going bald.
According to information in the books ''The Shadow Within'' and the ''Passing of the Techno-Mages'' trilogy, Morden had a wife and daughter that were supposedly trapped, fully conscious, in a bubble of hyperspace after the transport they were travelling in exploded ( which the Shadows offered to end with merciful deaths in exchange for Morden's services to them). Knowing this, one wonders if the man Bester's apprentice "spaced" (in hyperspace) in the episode "The Corps is Mother, the Corps is Father" suffered a similar fate—conscious but trapped in some sort of eternal (or very very long) limbo in hyperspace, with no way out. We don't know much about the properties of hyperspace, but it seems that under some circumstances anyway it is liveable. And we know that Psi Corps or their agents have used lifelong mental tortures as punishment (a la the fate of the serial killer of telepaths which Lyta described in another episode). Imagine being trapped, forever, in that weird and unnerving soup that is hyperspace....
Delenn outlives every person who mattered to her, except maybe Vir, likely including her son. Marcus, Londo, G'Kar, Sheridan, Ivannova, Garibaldi, Zach, Lyta, Lennier and all dead for certain, it's stated something very bad happened to David Sheridan, possibly killing him as well, leaving only Vir in question. And not only are they dead but her loved ones sacrifices are being forgotten and insulted by the current generation. No wonder she's spent decades in seclusion.
David had a Keeper put on him on his 16th birthday from the gift Londo gave Delenn and Sheridan, requiring them to return to Centauri Prime where Londo dies.
David is still alive as of "Sleeping in Light" when he's an adult and serving as a Ranger. Given that humans routinely live over one hundred years by this time, he's likely to still be alive unless something has happened to him. Delenn may even have grandchildren and great-grandchildren depending upon how compatible David's genetics are with either humans or Minbari. However, Vir likely is not alive if the timeline given by Galen in "The Lost Tales" holds true. Galen states that twenty years in the future (from 2271) Prince Vintari will take the Centauri throne. Londo reigns for 18 years, which means that Vir gets 12 years as emperor. Of course, since Sheridan's actions altered the timeline, Vir may still be on the throne by that point, to be succeeded later by either Vintari or Vir's own son. Given that the academic panel in "Deconstruction of Falling Stars" didn't mention anything about a war with the Centauri in the hundred years since the founding of the Interstellar Alliance, it's likely Sheridan's plan of influencing Vintari to be less hostile toward Earth worked. And, given that Sheridan and Delenn fostered Vintari, it's likely she formed a bond with the Centauri prince as well. And these are only the people we see on-screen: Delenn has her own blood relatives, fellow Religious caste members, etc. So Delenn isn't as completely without emotional bonds by that point as one might suppose, although it's understandable that she'd take extreme exception to those who'd run down the legacy of her loved ones.
In the episode Intersections In Real Time, the interrogator mentions that he takes a little bit of poison daily, so that he gradually builds up an immunity. He feels it is a metaphor for something, but he can't quite think of what it might be. He spends the entire episode declaring (entirely unironically) that the Truth is entirely arbitrary, and trying to bring Sheridan around to admit that. He has been touting Clark's propaganda for so long, he seemingly believes it by now, even as unbelievable as it seems to Sheridan and the viewers. This of course, blinds him to the very metaphor he is trying to explain. It's pretty much the only time in the episode that he seems to falter during his battle of wills with Sheridan.
Micheal Garibaldi, the brilliant security chief, failed to realize that forcibly seceding from the Earth Alliance would result in a disruption of his postal service? The same postal service provided by the Earth Alliance? Seems like a bit of an odd blindspot for his deductive skills.
I don't think he had missed the fact that postal service would be disrupted, he was just pissed about the extra fees.
In "A Late Delivery From Avalon," Marcus proposes that Mckintyre might actually be the real King Arthur, preserved by the Vorlons in much the same way that Sebastian a/k/a Jack the Ripper was. Franklin objects, saying that 'Arthur's' speech patterns are too modern by about 1400 years. A very logical objection...except that Sebastian's speech patterns should be about 350 years out of date as well (of course, the only major character he interacts with for a significant length of time is Delenn, and their entire conversation may have been in Minbari). Consider how well Shakespeare's works or the original King James Bible holds up for modern English readers to see what a difference this should make.