I commented on a community post by the creator of Prehistoric Emergence (an analog horror on YouTube) and they actually REPLIED! and it led to us sharing ideas and geeking out over their worldbuilding.
I used to hang out in the Tumblr rp community and before that, the LiveJournal/Dreamwidth RP spaces, and I've made so many friends either because people saw my rp threads or I saw theirs and comments were made.
I also made a comment on one of Jesse Cox's Scary Game Squad videos in their RE9 let's play, where I clarified the interior decoration type they'd been debating in the episode. It got a LOT of attention, more than my YT comments usually do, including from one of his mutual friends who stopped by to thank me for the injection of positivity.
yes, you might only see a handful of results out of hundreds of comments you make (if you're terminally online) -- but they're all well worth it.
engagement and silly comments and fun little notes on random websites in the backroads of the internet is what the internet was BUILT on.