This is very eloquent. I balk against OTPs, myself (unless I'm jesting, mocking, or otherwise being a smartass), and I'd never heard of the LBD syndrome until you mentioned it. Both are a huge problem in roleplay as well as fanfiction (over-identifying kills the writer, imo), and that's one of the reasons I strongly encourage roleplaying and writing from perspectives across the spectrum ("write as a villain, write as a hero, write as a victim, and then write as a puppy or a five-year-old -- it'll be good for you, honest"), that is, if anyone ever asks me. Which they never do, unless they unwittingly stumble into an RP conversation with me. I should have warning signs around my AIM name. "Don't mention OTPs to this woman..."

I'm not sure how possible it would be to separate oneself from an LBD character, however, once you've identified that strongly. Is it even possible? And is this the same or similar to the complex which occasionally makes us cringe at another person's (or even the original author's) portrayal of a character when said portrayal differs or contrasts our view of him/her?