Zap Brannigan: Would you like some...shampagin (champagne)?
Leela: I never knew you were such a coinasewer (connoisseur).
The coinasewer is someone who believes themselves to have refined tastes, but they really don't. Basically. A coinasewer of literature may use terms like "good writing," or "character development," but they don't expound on how those terms apply. They might consider a Blood Knight to be a unique character, despite the fact that it's one of the more common archetypes, at least in anime.
Note, this isn't about what the character likes, or whether or not it actually is refined. The mark of a coinasewer is a profound ignorance of standards he's trying to examine. Note the page quote. It's not that that he likes champagne, or the champagne itself, the problem is that the coinasewer doesn't actually know anything about champagne, and is merely playing at being cultured and impressive.
As for why the coinasewer is what he is, there are various reasons. Maybe he's an opinionated individual who just isn't very good at promoting and defending his ideas. Maybe there's someone he wants to impress. Maybe he's not very smart, but with a large ego. Ultimately, though, the result is more-or-less the same.
Compare with the Hipster.
Zap Brannigan: Futurama. The Trope Namer.
Omaeda: Bleach. Despite frequently flaunting his wealth, he's generally an ill-mannered slob.
Deidara: Naruto. Your Mileage May Vary on his art, but despite touting himself as a great art critic, he makes little attempt to acknowledge art that is not his own.
Brian: Family Guy. Most scenes that mention his authorial ambitions hint not so subtley that he's actually not much of a writer.