I am not sure whether LW is over-moderated. How would one tell, apart from personally feeling intimidated?

I'm using the word "intimidation" to refer to any kind of aversion to posting more stuff associated with getting downvoted or criticized. Obviously, a huge reason that downvoting does anything is because people don't like getting voted down, and when they do get voted down, they work hard to avoid behaviors resembling the one that caused them to get voted down. They will also tend to avoid behaviors that they saw other people get voted down or criticized for.

Empirically lots of people report feeling intimidated.

I don't think there's a reluctance to spend time writing longer-form stuff: many LWers write blogs. On Less Wrong, though, there is a bit of a culture of "how dare you share that with us", "how dare you put that in Main and not Discussion", "is this really appropriate for Less Wrong", etc. (as seen in this thread and elsewhere). And unlike reddit, where your submission is silently downvoted in to obscurity, on LW it's pretty public that you screwed up since item scores impact visibility less. This leads to a gradually reducing trickle of submissions to Discussion and Main, and then people say things like "Less Wrong is gradually running out of things to talk about" (more like we're all becoming conformists who don't introduce new topics because they "might not be appropriate for Less Wrong").

Potential fix: have a single subreddit (with a less-trafficked "new" section) so that open thread posts/discussion posts/main posts are all part of the same system and the userbase collaboratively decides how much visibility your post gets (which makes screwing up less public, and solves the "discussion vs main" problem for short, speculative essays like you see on Overcoming Bias). In the extreme, go upvotes-only (kinda like Hacker News).

I really think that LW has overcorrected for the eternal september problem--if anything, seems like the quality of Main posts has gone up drastically since the site's creation (with a corresponding decrease in their frequency). Maybe it will be the next generation of online forums that finally get things right :)