So this is something I noticed in many of those fanfic "pet peeve" threads, and complaints about characterization OOC-ness (particularly if it involves character bashing) is one of the most prevalent complaints.
But sometimes, the premise or setting of the fic does require the character to be somewhat OOC (e.g. a character is demonized to justify a pairing or angst, another is dumbed down for the sake of comedy, etc). What I want to ask is, how far can one stretch the characterization and justification before the character becomes completely alien this OOC-ness become unbearable?