I don't think the problem is with trolls and spammers necessarily, I think the problem is with scaling the community out. 4chan is the best example of this: the less populated, hobby-based boards are wonderfully useful resources and generally of much higher quality than similar communities on Reddit. Reddit is just too big and the clout-chasing inevitably infects smaller subs.

The larger 4chan communities like /b/ and /pol/, on the other hand, are irredeemable cesspits compared to Reddit's default subs.

I second this, I frequent the /lit/ (literature) board on 4chan and its really good. It's still quite irreverent but its good when studying philosophy, where it was always rebellious (e.g. Nietzsche's "God is Dead").

> Voting certainly has its problems, but the alternative is [giving] trolls and spammers free reign.

I would replace "voting" with "moderation." Voting mechanisms on conversational sites are a form of moderation; so are actual moderators. And, of they're not mutually exclusive.

> Even in its current state, I find Twitter borderline unusable, because > 95% of posts are worthless noise.

I think Twitter tried to replace moderation with curation -- in theory, you're only going to see posts from people you follow, giving you direct control (and responsibility) over the amount of noise on your timeline. In practice, of course, Twitter goes back on that implicit promise in the name of engagement. Twitter itself injects things you don't have direct control of onto your timeline -- not just promoted tweets, but "people you follow liked this" and "someone you follow replied to this tweet" and other such dubious nonsense -- and also lets people you follow inject things onto your timeline through retweets and quote tweets. But, I think the original idea of "give you the tools to curate what you see" was relatively sound, although it should have implemented LiveJournal-esque "only allow replies from people I follow and/or who follow me" type filters very early.

IMHO, that was more a result of the very high barrier to entry to get access to the internet, than its size. I still fantasize about creating a community with such a high barrier to entry today, but where it is done better than just making it depend on your technical chops and internet connections in the mid-nineteens.

You can have voting mechanisms without their results being visible. It isn't very transparent but social media is still curated and moderated by platforms regardless of "voting".

It didn't work in the past. Usenet groups were like that and they got eaten by spammers and trolls.