>One of the last examples I remember is about 18 months ago I noticed everyone, everywhere, as if coordinated by some unseen entity, started replying "oof" to everything. Maybe this really is just a variant of the Bader-Meinhof phenomenon (another one of "those little memes" you mentioned, heh).

Maybe but I think it is just more social signalling, to either show you are part of the opposition or to highlight the comment for like minded people. Similar to other comments : Yikes, Wrong side of history, a bad look, etc. Most of these comments are made on highly political threads, highly controversial topics such as system-d don't seem to evoke these kind of comments. That leads me to think that they are more emotional in nature than analytical.