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SomethingAwful's forums required a paid membership and have been around a long time. IMO one of the points of a paid model is keeping membership down to people who actually care enough to pay said membership.

Additionally, the implicit threat of having your paid membership revoked for bad behavior can provide a natural check.

Something Awful has used this to great effect to keep trolls in line. I wonder what % of their membership revenue comes from banned users purchasing new accounts.

I'd say most of it, at this point. As a long-time goon, getting banned and rereging the account is a way of patronage. No joke, it's very common behaviour there.

In addition to the examples posted, this model also worked well for MetaFilter. Some of the highest quality online discussions I've seen.

TED and ACM

https://www.ted.com/ http://www.acm.org/

ACM is a professional association, and I wouldn't consider TED a community.

Neither of these is anything close to a subreddit or forum which is the "community" to which the thread is generally referring.

I would think that LWN is a good example.