Although in theory every argument could get a counter-argument (or a request for clarification, or whatever), in practice people seem to have some "time budget" they want to spend on a specific discussion, and they leave when they run out of time, and maybe get impatient when they see the time is running out and the topic is not yet solved. My impression is that people who seem to be mind-killed often write a lot. For example, there could be a discussion where some twenty people write one or two comments each, and then there are two or three people who write dozen comments each, defending a minority position. And of course, being in a minority position does not necessarily mean being wrong. It's just, when I see someone writing 10 comments, replying to 10 people who disagree with him, I feel like what's the point of joining this? If 10 people didn't convince him, what is the probability that I will? And I feel like the person has decided to spend much more time on the topic that I would like to. And "dude, you already got 10 explanations why your position is wrong, and yet you keep posting the same thing, maybe reflect on that first?" meta comment is... well, almost an ad hominem. (In terms of user interface, perhaps there should be some way to say "my objection to your position is already expressed in a comment written by a third party... so instead of writing my own comment which would essentially state the same thing, I would like to see you address that comment". Not just upvoting the comment, because that just means you liked it. But something like "your response to that comment is my condition for participating in this debate... because I would pretty much write the same thing".)