A "fun" experience from Reddit that I'm glad is impossible here on kbin is when I'm in an argument with someone and they would insta-downvote every response I made to them, then vociferously deny that they were doing it even when it was basically impossible for it to be otherwise (for example if we were in a days-old thread nobody else was paying attention to and the downvote was happening within a minute or two of me posting - too fast to even have read the comment).

On a related note, I'm pleased that blocking someone doesn't prevent them from responding to your comments here. The "get the 'last word' in and then block me so I couldn't answer" pattern was even more annoying, since karma was meaningless anyway but the block disrupted the flow of informative debate if other people were following it too. In such situations I'd edit the last comment I'd made to mention what had happened, at least. Hope that shamed a few folks at least a little bit.