It feels like a sort of Internet-speak affectation (something I know a thing or two about) that wouldn't show up in spoken language or other forms of written language. I can see how that would bug people.
I doubt age has anything to do with it. I'm 38, but I don't dislike the "this" thing much at all. In fact, I do it myself sometimes.
and I frown on people using my language in a way that diverges from how I've always used it.
See, I'm the kind of person who likes doing things differently, just to irk people like you. I don't see much value in blind adherence to tradition for tradition's sake. I like killing sacred cows, stirring the pot, ruffling feathers, and reminding people that "We've always done it this way" is not a valid justification (in and of itself) for doing things a certain way.
Then again, I'm a radically individualistic anarcho-capitalist / libertarian / atheist type, so I'm just a touch outside of what you might call mainstream...
To me, it's more like "if you use words in a way that diverges from what people can reasonably expect, nobody can understand what the fuck you're saying"