If you're having problems using Reddit through Tor, use HTTPS. Better yet, force the HTTPS redirections in the Reddit settings.
This info is, of course, redundant or too late for the people talking about illegal activities on that particular subreddit, but it might come in handy for when they come searching for you.
I believe he's saying that accessing Reddit using Tor with HTTP is sometimes problematic but using HTTPS can fix the problems. (It's been a while but I think that might mirror my own experience.)
That's correct. Last time I tried it, Reddit was borking HTTP POST requests made through Tor. Now they seem to redirect everybody to HTTPS after login and the problem is solved.
This info is, of course, redundant or too late for the people talking about illegal activities on that particular subreddit, but it might come in handy for when they come searching for you.