Here's my theory on why “discussion detaches from the issue at hand, turning into meta-debates about how we respond to the responses of others, etc.”: I think

Here's my theory on why “discussion detaches from the issue at hand, turning into meta-debates about how we respond to the responses of others, etc.”: I think it's a battle for common knowledge (See: https://scottaaronson.blog/?p=2410 https://scottaaronson.blog/?p=2410). Suppose there are two groups, A and B, having a different stance on a given issue. On social media, it's not enough to voice an opinion about the issue at hand. Because the nature of social networks make it easy for opinions that are globally rare to be overrepresented (see: The Majority Illusion In Social Networks — https://arxiv.org/abs/1506.03022 https://arxiv.org/abs/1506.03022). Therefore, if you're from group A, you want to make sure that your opinion is common knowledge, but also the fact that you're shunning indivduals from group B (to signal that they are a minority or on the wrong side) common knowledge as well. That's why the discussion drifts quickly into those meta-debates.