It's very nice for what it is, but it's not a counterexample to the problems with reddit because /r/AskHistorians achieves its famous reliability by outsourcing user authorization to the university system (you must be a historian to answer). This is not possible for any subreddit centering on a topic which is not famous enough to have entire departments of universities about it, such as, for example, Super Smash Brothers Melee for the Nintendo GameCube.
This was a fun thing when Starcraft 2 was new and it seemed like literally everyone on the /r/Starcraft reddit page was "high Diamond" league. (Diamond was still the highest league at the time).
Considering that only 25% of all players are in Diamond league and the game has no way of telling you whether you're low or high within the league, this was clearly bullshit. But everyone on the forum very desperately needed to validate their whining about "balance" by putting a veneer of being "skilled" on it.
In general, there are good subreddits that sometimes develop community spirit. Unfortunately they are a fleeting phenomenon: either they grow too big, or die off (or in the rare case of AskHistorians, become something that can manage the flood), and if you don't find them by accident, it probable one heard about them because they are becoming too popular.