The 90/9/1 theory is fairly commonly mentioned but I have never seen an authoritative paper about it. Did your class provide a source for that? I might make a post a week here and comment almost everyday. On voat I try to make three posts a day to this little subverse I created and rarely anywhere else. (3 posts and 3 explanatory/source comments) On reddit I made at about 100 comments a day but it was 99% moderator activity. On snapzu I probably post or comment a few times a week. Hackernews almost never since I have very little to add as I am not a programmer etc. There can be occasional spans of days where I do nothing but observe, usually when I am super busy or feeling burnt-out.
I think you are right but I don't even have an account there any more. Now I just lurk here. :)