Fair for Its Day: Dorian and Burma came come across as somewhat as bigoted caricatures to modern readers. But Burma is clearly portrayed as a victim of Police Brutality, and Dorian is never portrayed as a villain.
Genius Bonus: Hroswitha, whom Ignatius name-checks a couple of times, was an actual person — a medieval nun and playwright whose works are mostly about chaste, pious women frustrating the schemes of lascivious men.
Mancuso. No matter what is thrown at him, he doesn't back down. Fortunately, it works out for him in the end.
Burma. The dude is harassed by police and made to work for a greedy boss. Yet he deals with these problems with surprising equanimity, and through Ignatius, he is able to deal with both of these problems at once.
Gus Levy. The guy had to deal with a nagging wife who puts him down constantly, and and his father was a stubborn idiot who refused any of his recommendations. Subtly, he is so idle because he simply doesn't care anymore. Ignatius' letter, however, helps him regain interest in his company again.
Jerkass Woobie: Reilly is perhaps the prime example of a non-functional human being in modern society, but he doesn't deserve all of the bad stuff that happens to him. Indeed, the more naive reader might at first mistake him for just another "sensitive" young Sixties activist - one who's a bit strident, but definitely well-intentioned. However, this characterization is undercut by the fact that Ignatius is only getting involved in social causes to stick it to his holier-than-thou girlfriend.
Mr. Levy himself feels sorry for him.
One True Pairing: Myrna and Ignatius are pretty much destined to get together from the get-go.
Squick: Anyone who stands still long enough will get a lecture on Ignatius' valve. When it closes, he tends to fart and belch a lot.
Values Dissonance: As this was written at the height of the Cold War, there is obviously a little bit of this.
In the end, Lana Lee is arrested for distributing pornography to minors, which is treated as her just deserts. She deserved punishment, but not just for that.
Toole paints his characters in very broad strokes, mining New Orleans stereotypes to their fullest in a way that would be considered insensitive today. Burma is a pot-smoking, sunglasses-wearing, Jive Turkey-spouting black man. Dorian Greene and his retinue of Camp Gay men and Butch Lesbian women are another example. However, Toole is going for Rule of Funny rather than putting anyone down.
Values Resonance: In the beginning, Ignatius goes into a rant on how corrupt New Orleans has become, listing off all the vice and crime going on there. In among things like drug addicts, prostitutes, and gamblers, he lists "sodomites" and lesbians. Of course, arch-conservative that he is (or thinks he is), he would probably say the same thing today. Part of this is because Ignatius is supposed to be an Unsympathetic Comedy Protagonist who thinks civilization took a wrong turn at the Renaissance, so having his views become slightly more out of date doesn't really change his characterization at all.