I don't know, I just had a few thoughts regarding the importance of writing characters In Character vs Out of Charcter. Thinking things through, I found myself puting down my thoughts thus wise:
Well on the one hand, it's impossible to write a Fanfict that's completely IC because you're writing about characters written by someone else. At the same time however, Fanfiction is in many ways a shortcut, allowing the writer to write a story without having to establish an entire cast of characters and a setting through their own writing. And since the writer is borrowing from another source, variants from that source have the effect of stopping the reader while they mentally compare the story to the original.
But there is a much more important criteria in whether or not a stories OOC-ness is excessive or not. Conflict. Conflict is one of the most important parts of storytelling, be the conflict emotional, rational, or a big brawl. The important thing to remember is that the source materials have their own sets of conflicts, and OOC writing is most infuriating when the deviation artificially resolves or eliminates a major conflict theme from the source material. EG: In Ranma 1/2, Ranma's Relationship with his multiple fiancees and his refusal to commit are the foundation of the main ongoing conflict holding the story together. The biggest complaint raised with OOC stories resolving the fiancee question, is that they altered the nature of this enduring and hard to resolve conflict, changing it into something that can be resolved in a couple of paragraphs.
That's what's really going on behind the OOC complaint, it's an objection to the apparently arbitrary elimination of a major underlying conflict of the series. Which leaves the writer being judged by the quality of the conflict they use to replace the original one, and their ability to manage the transition from resolution to new conflict.