Posts like this have been written before, but I think it's worth making the point periodically.
Lurker ratios have likely increased over time. Comments and discussion are an important feedback mechanism for content creators. So if you see stuff you like, and you'd like to see more posts like it, it's quite helpful to comment. Many people report being intimidated about posting, especially if the platform in question has a highly specific vocabulary and norms. I wanted to offer a couple of the heuristics I use for making comments as well as invite others to boggle/comment/discuss what they think mediates the difference between times they do and don't comment.
In a shallow review of the pedagogy literature, four interventions stood out as having large effect sizes replicate: deliberate practice, test taking, elaborating the context (cross linking knowledge), and teaching the material to others. Cross linking provides an easy heuristic for commenting: simply mention which idea(s) in the post stood out to you most and how they connect to your existing knowledge. This helps you by strengthening those connections, and helps others because each person's cross links have some chance of being unique and therefore surprising to others. I think of this as a sort of low rent version of helping the post author cite additional sources. And speaking as a writer, these sorts of comments are always welcome as I learn about which ideas tend to stand out the most to people and might be worth writing more about.
Another heuristic I've found quite helpful is just to say more obvious things on the margin. Due to illusion of transparency, many things wind up being less obvious than I thought. This also forms a bit of a virtuous cycle as it helps reduce the context overhead for other readers, giving them more on ramps to comment and discuss. You will pay a minor cost of people occasionally getting frustrated that you're repeating something they already know about, but this happens much, much less often in my experience than people thanking me for alerting them to some concept that they either were only somewhat familiar with or had never heard before. This doubles as good vulnerability practice, creating more opportunities to connect with people over odd corners of mutual interest.
I think it's worth it to try over correcting here. I have had a surprising number of experiences of people telling me I was the first person to thank them for something that I imagined was popular enough for them to get lots of feedback on.
Please feel free to comment on things that have made you feel better about commenting, or if you're an existing contributor what sorts of comments make you feel most appreciated for your writing efforts.
P.S. I waffled about making this post, then realized that was kind of silly.