That's odd. I've only mostly lurked here. Does that happen when you're a new poster or something? I've only had a handful of posts. I hope I didn't break any rules.
If you have showdead on and see a dead comment you think is worthwhile, you can click the "vouch" button to reanimate it. That may have happened in some of the cases you're seeing. IIRC, I vouched for https://news.ycombinator.com/item?id=13126780 after seeing your earlier comment.