It's not the right kind of time, though. Reading and occasionally posting usually don't require sustained concentration -- they can mostly be done as a break from that. (Of course there are times when an interesting and difficult topic shows up, or a debate arises that one wants to participate in.) So for the most part, it's a break from work. Switching from one nontrivial technical task to squeeze bits of a much more difficult task into one's day is much harder.

Are you seriously claiming that making posts on Hacker News and Reddit requires anywhere near the intellectual rigour and deep thought required for "paradigm-shifting" changes?