That phrase may have overestimated the number of such subreddits - I mainly read r/Singularity (moderated by MIRI people, similar to LW, low volume), and r/artificial. There is an r/agi but it is very low volume. r/futurology is very high volume and future-optimist.
r/machinelearning is the most serious and the AMAs there are pure gold (Hinton, Bengio, Schmiduber, Lecun, Ng, etc). It's main value for me is making it easier to stay up to date on ML/AI, saving most of the trouble of having to read through tons of abstracts from the various conferences.
/r/Futurology is also really annoying because people keep having the same arguments over and over again.
My post on the fact that incentive structures are eating the central place to be for rationalists has generated 140 comments which I have generated no clear action in the horizon.
I post here again to incentivize that it also generates some attempts to shake the ground a bit. Arguing and discussing are fun, and beware of things that are fun to argue.
Is anyone actually doing anything to mitigate the problem? To solve it? To have a stable end state in the long run where online discussions still preserve what needs being preserved?
Intelligent commentary is valuable, pools are interesting. Yet, at the end of the day, it is the people who show up to do something who will determine the course of everything.
If you care about this problem, act on it. I care enough to write these two posts.