For me, it’s very much an allergy to romance in general (which applies to real life as well, to my husband’s occasional despair). I don’t see the pairing that other people do, and automatically read close bonds as familial/friendship rather than romantic. I think some of us just have our brains wired that way! It’s kind of amazing I managed to get married... honestly, I don’t mind fic with pretty much any pairing, but it has to be exceptional to make me interested in the pairing alone - I need at least a semblance of plot. The only exception I can think of is Junk Cheap, and old SGA fic, but the writing in that was enough to lift it for me.

Heh, yes, it’s funny how what we like to write and what we like to read can be so different! I tend to avoid modern/mundane AUs for magical or sci fi fandoms, and I’ve read enough Daemon AUs that I tend not to bother. I’m intrigued as to what you mean by getting too close to the second canon. Do you mean it pulls the people from the first fandom out of character?

AUs are tricky things, which might just be why I like then so much. It’s so satisfying when the author pulls it off!