Well, I often get quoted by people arguing with me (or sometimes agreeing, but there's not really any way to respond to those). If I didn't respond shortly after the post, the person may think I've given up, maybe even accepted their point of view. They may think they are correct, or that their points were completely valid, and that I was unable to think of counter-arguments.
If try to sleep I'll see them sat there, with a smug look on their face, mocking me in the night while I try to force myself to drift off...
Force myself to just forget about the points I was going to make...
Force myself to let them win...
...
This is not acceptable to me.