One is the original weblog model, with either no comments enabled or with some sort of whitelist comment participation. You can write whatever you want, and some asshole over there can write about how stupid you are, and it doesn't have to bother you unless you deliberately visit the asshole. Back before social media, there were cases where there were entire weblogs devoted to replying to literally every post some other weblog made, but nobody cared except the few who deliberately sought that out, because you had to go out of your way to visit.
I suppose I should point out explicitly that my goal is not to create a 100% comfortable world in which you never encounter an asshole, but to create something a bit more like the real world where by the time you're an adult and you've found a place for yourself in the world, by and large you probably don't have a problem dealing with lots of people-you-consider-assholes personally. (You may professionally, but that's a different sort of problem.) Even if you maybe have a problem with one or two people in particular, you almost certainly do not set a foot outside your bedroom door and immediately get several thousand people screaming at you at the top of your lungs. But you're going to encounter a few, sure.
More on the Reddit model, I outlined something here: https://news.ycombinator.com/item?id=16570017 The observation that it is computationally expensive is true, but I'm not convinced it's intractably so. There the idea is that if some anklebiter starts replying to your every comment, by default you at most see something greyed out or collapsed if you did not have any previous connection to them, and they can't bother you. I think to jumpstart the system you'd always have to have a couple of random comments show up, and some of them may be assholes, but it wouldn't be the case I was describing where you can get this unrelenting torrent of abuse.
(I think such a system would have more manipulation resistance, too. $MEDDLER could go to some political forum that works that way, and maybe they could convince a few people or a subcommunity to upvote them, but they wouldn't be able to completely take over an entire topic by sheer mass the way they can on Reddit. You can't get a world where $MEDDLERs don't exist, but you don't have to have a world in which only $MEDDLERs and $MEDDLER-approved accounts exist on your forum.)