I didn't mean earlier members as in people who joined HN in the early years, rather I meant the people who tend to react and comment within maybe the first 30 minutes after a post/comment.

I actually find the early members (as in the early 2010s and before) to be among the best. I have no idea if they are downvoters or not, but some of my favorite conversations on HN have been with these users.

As far as sourcing, definitely take with a big grain of salt because this is also purely anecdata that I've noticed from spending way too much time on HN, both repeatedly having my own comments downvoted initially while (usually) rising up over time, and observing the same phenomenon on many other people's comments.