And the obverse is r/sanfrancisco with moderation that has turned the sub into a sunset travel pic slide show punctuated by golden gate bridge pictures. What a wasted opportunity for something interesting. And it is leaking into r/bayarea ruining it as well.

Interesting phenomenon. It's eerily similar to r/Boston.

You overestimate the skills of moderators... I doubt very much that true experts in their fields would spend any time doing moderation Reddit... most likely, people doing that would be recent graduates trying to learn and impart their recently gained knowledge upon laymen.

There are several subs I'm aware of which do seem to garner expert-level moderation.

The Asks -- Science, Historians, possibly Economists (I'm trying to decide there -- the mods talk expertise, though quality IMO lags). Several of the Fitness subs are quite good. Various technical subs attract high-quality contributors, and the CSS support sub (specifically for styling old-style Reddit custom stylesheets) is simply superb. I've dug into energy topics, and though there's a bit of BS flung about, there's also quality expertise.

Posting online actually is a form of shingle-hanging and getting a sense of issues people are facing in the real world. There's value to that.

I wouldn't use science as a paragon for moderation, they were involved in a huge vote manipulation controversy just last year

/r/askscience is well moderated.

Within a narrowly defined range of acceptable debate (see: Noam Chomsky)

I feel like I've seen more of the opposite (piss poor moderation) than the good. This is why on your average subreddit, the average quality of discussion is extremely low, with the top comments being low-effort one liners. In worse cases, sometimes the moderators because straight up authoritarian, censoring opposing views even if they're well-reasoned and thought out (any politics-related subreddit).

I'm not defending reddit at all, however to be fair certain topics are almost guaranteed to have very heated comment threads, politics for example.