As far as I know gay meant happy ONCE. But the other way around, never heard of it until now, and I'd simply guess it's a popular confusion, but nevermind.
I doubt it's possible to change the situation at THW. In my beginning, I had my expectations bruised by dumb remarks and trolling from some users, and some other things.
Those things got better after I killed them. Yeah, I mean I killed my expectations, obviously not the users.
But gloom is just a hiding. You can't really tell people's emotions or personality out of gloom. One can be unhappy, pretending to be gloom-cool, one can be happy, hiding it so to be gloom-cool, or one might be neither, and really be like he/she seems. I can't tell. But ultimately, people can hide in gloom, and so what's the point in that?
I dunno. I think THW has gotten to me sometimes. I act very unlike myself here. I check out of habit. It's a breather. After a month of absence, I can return and feel good seeing that the users are having the same sort of discussions.
Take my view for what you will. I'm actually in good mood near always, however gay that sounds (and is there a big problem with homosexuality?), and I'm sure you'll meet more (gays or happies

. But I can understand your observation and as said by some of the others, it's an attempt to seem cool or grown-up.
And it's frankly way out, but isn't RL(tm) (of which THW apparently isn't a part) that too?