The only reason it sounds socially unacceptable right now is that when you're younger, age gaps look worse. If you guys hadn't met online, I wonder if you would've hit it off as well initially. :O It's much easier to ignore an age gap if you know someone mostly through text at first. (And especially through fandom!) But I find irl it's a bit more awkward just because the typical stuff you talk to people about is usually standard like school or work and if they're juuust young enough that they can't relate (or vice versa) then it's kinda weird. And that's probably just the only way your friends see it.
But in a year or two the gap will mean nothing anyway. XD; Four years is nooothing when everyone's a little older, haha. Even ten years doesn't seem weird between most adults.