OTOH Reddit also enforces time as a limitation on posts, just on a slightly slower scale than Facebook.
For example "necroposting" isn't really a thing that's possible with a Reddit (or HN) model. Nor are threads that are ongoing for months at a time, which are quite common on traditional forums. I mean you can do it but it has to be mod-sanctioned via pinning.
I think you're being a little bit disingenuous here. Not everybody only subscribes to a bunch of niche subreddits with good moderation. A lot of the larger / less strictly moderated subreddits are filled with toxicity, bots, and other nonsense.
For example "necroposting" isn't really a thing that's possible with a Reddit (or HN) model. Nor are threads that are ongoing for months at a time, which are quite common on traditional forums. I mean you can do it but it has to be mod-sanctioned via pinning.