I think Buffy fandom benefited from the fact that there was such an amazing ensemble cast and that the writers really did have everyone interacting with each other. It made it easier to have a foundation to write any pairing without it seeming completely OOC. I remember writing Oz and Ethan and feeling like it made sense because of the way the show worked in canon.

I wish we could get this in Vampire Diaries because I see the same type of potential there, but it just doesn't seem to have caught on. But a lot of writers came to Buffy late, so maybe there's still hope. We shall see.