[krapp]

The forums I hung out on simply sorted by the last comment, or by votes. They certainly didn't "optimize for quality content" in any particular way, other than banning trolls (sometimes.)

Also plenty of good forums had ads. I don't think it's a common thing to want to refuse to click on ads because of high quality content, I would guess the opposite tends to be true.

[Lucadg]

I probably have a too much romantic memory of them :)

Anyway, it was easy to come back to a specific topic, so it was easier to find good ones. You could bookmark them, see the number of views/replies or even find them in search engines.

Good content surfaced and survived better, so optimization is probably the wrong word.