Humm, I guess I might as well add to the lists of reasoning behind choices...
Affinity and confirmation :
Well, I guess I picked this because this is pretty much the one place I know about where you can say something that everyone you know in real life thinks is weird and actually have people who share it with you, which is still pretty much new to me. I like seeing just how similar we are, mainly I guess because it's more confirmation that I'm not an alien after all (Or, we're all aliens and I've found more of my kind =P).
Funny tangents and witticisms :
I do like this, but only when it's appropriate. In the more serious threads, then I would be annoyed to see this happen, although in other places (The arena springs to mind) It's interesting watching how the thread evolves from one thing to another.
Questions, Challenges and critiques and Expansions on your post :
I like these mainly because they help me to refine my thought process, to work out exactly what I mean again, and by doing it at different times (Which I often don't have time to do, or I forget or something) I can work out if I've said something wrong, or I might find a better word for what I wanted to say and so on. Plus, theres always the very likely chance that someone's found a way to say what I wanted to say in a much clearer way.
Grammar, syntax, and language corrections :
(Yep, it was me that picked that =P)
Mainly because I was thinking of my attempts in the language thread, and so I was thinking about how if people help each other with grammar and so on there, then it'd help us all to get better at it. (Of course, this now gives you all the excuse to point out every single mistake I've ever made =P)
Some other option I should totally have thought of... :
Well, I have to say I like it when this happens, as it's like a brand new way I can look at it, like getting a load of new information on how it all works, so I can change my opinion of it to fit, or at the least, it might help me to understand the person or the problem/question better. Plus, it's another shift that opens up a whole new area of the conversation, and I have to say, reading everyones posts on a topic is always interesting =P