Dueling Scar: As might be expected given their dueling tradition, Lutan has a large scar on his right cheek, while his subordinate Hagon has a slightly smaller one on his left. Apparently the men don't poison their weapons.
Early Installment Weirdness: This is the first time we see the holodeck in its off mode. Here, the floor is a gray carpet rather than the yellow grid.
Exact Words: The fight was "to the death." Not necessarily to the permadeath. Yay for Crusher, she class-upped to Necromancer.
Informed Ability: Lutan goes on and on about honor, but he kidnaps a foreign dignitary, holds her hostage, wants to force her into marriage, and the only reason the other side puts up with his crap is because he's got something the other side wants that can save millions of lives, and they're at least nominally not the kind to engage in plunder on an inhabited planet even though the Enterprise alone may be more powerful than his entire civilization. He's little more than a bully and only gets by because the other side has honor, and not a warrior code kind of honor. If he tried to pull this crap with the Romulans, Cardassians, or Klingons, he's either be assassinated and replaced with someone more pliable, or they would conquer him and chop his head off with a bat'leth.
It's a different form of honor, external reputation instead of an internal code. Sort of like the difference between normal Klingons and Worf. For instance, Data compares the kidnapping to counting coup; it's supposed to be a ballsy act against a superior opponent to prove his courage. The forced marriage is a bluff (after the fight Yar turns him down with no fuss), it's just that his current wife is so incapable of believing anyone wouldn't agree to marrying him that she falls for it.
Picard: By our standard, the customs here—their code of honor—is the same kind of pompous, strutting charade that endangered our own species a few centuries ago. We evolved out of it because no one tried to impose their own set of... I'm sorry, this is becoming a speech.
Troi: You're the Captain, sir. You're entitled.
Picard: Hmm, I'm not entitled to ramble on about something everyone knows. Carry on.
Revival Loophole: Yar must kill her opponent, but no one said she has to stay dead. As a bonus, this invokes the "'til death do us part" clause of Yareena's marriage, and she promptly picks Hagon as her "first one" instead. Oddly enough, it doesn't work in Lutan's favor as he doesn't inherit Yareena's wealth after she dies.
Schizo Tech: Ligon II looks centuries less advanced than current day, but it's capable of creating a vaccine that the Federation desperately needs.
Less unrealistic than it may appear, given that many of our modern medicines originated with herbal preparations (aspirin from willow bark, for example). The ingredients must be native plants unique to their world; maybe to them it's a simple headache remedy and the life-saving properties vs. Anchillean fever are a side effect. The Ligonians were explicitly compared to the ancient Chinese so perhaps they have a similar system of herbal and natural medicine.
Spectator Casualty: During a fight, an onlooker is killed by a flying poisoned spike glove.