It's well-known that there are levels of engagement with content, with fewer people doing the more involved things. Most people just scroll past everything. Single digits percentage upvote posts. Fewer go into the comments, and again maybe 10% of those participate in comments. The ratio of every level is different on different platforms, but it's there.

For platforms with pretty quick flow like Reddit and Lemmy, the ratio naturally falls off hard. Something like Hacker News rewards slower and more thoughtful engagement with content and threads, so I'd guess they have a larger share of active commenters — although OTOH you don't quite want to show up with mindless predictable comments like prevalent here.