I find it nice to know that someone agrees, and at times someone will have said something that just encompasses every single point possible to make, and there's literally nothing left to do other than to agree or to re-hash what they've just said.
Which in some cases is just as annoying.
If I find myself agreeing and I don't have much more to say I can usually squeeze out a post that is atleast something to read.
Even if it's not giving extra mass to someone's point, it's still arguably better to explain why you agree with someone and back them up that way, rather than just post 1 word.
But I've seen "/support" and "[quote] 'This' " ever since I joined.
It would be nice if it changed, but these forums are so casual that I don't think they ever will.