Some time ago, I was browsing the net and I stumbled across a discussion in which someone (I can't remember if it was on Snapedom or somewhere else...) basically laid out four levels of characterization in fanfic, in order from most in-character to most OOC.
Level 1: Citable in canon
Example: N Harmonia Gropius is childish and loves pokemon.
Level 2: A reasonable extrapolation
Example: N Harmonia Gropius hates to see anyone suffer, though he puts pokemon first.
Level 3: Weird, but not totally out of the question
Example: N Harmonia Gropius wants to have lots of sex with, say, Hilda.
Level 4: This character would never do that!
Example: N Harmonia Gropius wants to force Hilda to give him an heir.
I don't know if the commentator created these nice, neat levels intentionally, but I feel like they should be adopted into discussions of characters' portrayals in fanfics more often, because they're really kind of awesome.