Hope everyone is having a happy, chocolate-filled Valentine's day! Sorry I've been away so long. I've had a cold that like the Vanilla fudge song keeps hanging on.
At the MFA residency there was a lot of talk about author and character. Several times I heard the comment, "Your character can't do that. The readers wouldn't like it." There is some truth to the statement. I couldn't finish American Psycho because I hated the main character and didn't want to be subjected to his evil thoughts any longer. But short of having a character who sits around thinking of new ways to tourture his next victim, how bad can a character be before the reader ditches them? I think pretty bad. Silence of the Lambs, The Secret History, true crime books, all have bad characters in them, but readers love them. And what about the just-a-little-bad things people do everyday? An instructor commented that a character shouldn't be too condescending because readers wouldn't like it, but I think that insults the reader's intelligence.  Everyone has flaws and if a character is snotty to someone who has been rude to them, I think the reader will not only understand, but could even cheer the character on. We've all said or wanted to say something snarky to a person who wishes us ill, and readers will forgive a character for being human (isn't that the goal anyway?). I wouldn't advise you have a protagonist who kicks puppies or have readers invest themselves in a character who starts out as a jerk and ends up a jerk, but I think they are allowed to have flaws, even major ones. People are ruthless, hold grudges, gossip, make bad decisions, and if we sanitize our characters too much to please the imagined reader, we all end up writing Pollyanna (and how many of you were crazy about that girl??) If the character is fleshed out and behaves as a) most reasonable people would under the circumstances or b) in a way that the reader understands (like why Enda drowns herself at the end of The Awakening) readers will go along.
The only situation where I think a writer should be cautious about making a character flawed is in serial novels. If a protagonist is unethical or too snarky, then  readers aren't going to want to spend a lot of time with them. I might be willing to do it ( I like House eventhough the character is generally unethical, mean and selfish, but he's funny and gets the job done), but many who read serial cozies or serial small town fiction want a nice person--they can be flakey, unorganized, and at their wit's end, but they have to be nice.
Ultimately, the writer has to determine why the character is misbehaving. If it is essential to the character's journey, then I say go with it. But it the character is being bad just for humor or a splash of action, then you need to consider the damage you could do to your character's relationship with the reader and the overall value of keeping the behavior. If you're writing for me, I like my characters bad, just not too bad.