I don't comment here often, but I'm generally interested in discussions of site features and metacommentary, like this. Comment rates involve a mix of social and structural factors, I figure -- and like I discussed on that linked post, I think Cohost comment threads currently introduce more friction than they have to, just by intending too much per comment. I think this makes people more likely to go make their own post than continue a comment thread for long.
Setting that stuff aside though, for me the decision to comment is also influenced by my impressions of the original poster. I'm okay with writing comments for strangers (obviously), but if the original post sounds really snide or aggressive, I'd rather just not deal with it. There's a fine line to walk here because I'm interested to engage with posts I disagree with, and at the same time, I want a reasonable expectation that people won't just hiss at me.
Like Donnie said, it's also easier to reply to posts if they've got some kind of prompt or question. Besides overt prompts like this one, I can also approach a post like an implicit prompt if it's about trying to solve a problem or identify a pattern, in which case, I can offer suggestions or additional examples.
One other thing that comes to mind... if I'm weighing whether to reply to a post, it can be discouraging to see that all other existing comments on the post have gone unanswered. Not that I expect anyone to be online 24/7 or reply to everything, of course. I just mean that if someone is interested in comments, I'd expect them to show as much by participating in the conversation. I'm not as inclined to leave a comment if I expect to be ignored.