I think they are referring to fitness-related advice on Reddit, but, yes, there are a number of quite high quality subreddits out there among the not so great ones.

AskHistorians is a bunch of PhDs doing quality write-ups with full referencing.

You can't compare that to r/fitness in the least.

do you have a phd in history to judge that? I said I wouldn't trust, I'm sure there is some good resources but they are mixed with bad ones, I just know that r/philosophy is a terrible resource for anyone studying philosophy