If someone replies to your post/comment...

Agreed.

I try to, sometimes there isn't much to comment on or I have commented and the discussion has just reached a natural conclusion.

This is why a "Thumbs Up" or "Agree" button would be useful. A way to acknowledge someone's post without having to write something which may be kind of pointless.

I'll try.

eh... when I throw up a comment, i've typically already said everything I have to say about the matter and am contributing to the thread as a whole. further comments tend to muddy my point i began with. when i choose not to reply i'm not ignoring the poster. i just feel everything that needs to be said is on the page already. including their feedback. there's also no point in filling up the thread with "agreed"s and "you're out of your mind"s. considering a lot of the threads here were begun on a defunct website and the users aren't even around anymore to engage, it makes me feel especially "screw it" about the whole matter.

"McCock"?

I try.

The worst is when you write a long post and then someone replies with just one word, "K".

Well it's not as simple as that though is it ? This is an anonymous board where we really have no idea who we are talking to. And not everyone here is always motivated by pure motives and good will to all. I have a hardened attitude due to years spent as an active IMDb Boards user and believe me there were a lot of bad faith actors on those boards.