I spent a lot of time in high school on PHPBB systems. I find it less attractive now, using mostly IRC plus some forums, though I don't frequent them enough to be a "regular". I absolutely hate subreddits - I generally find specific enough ones to be of low quality compared to the equivalent forums.
I also absolutely love Futaba-style imageboards - it's a great blend of anonymity, simplicity, and community. It's a shame 4chan's reputation is what it is.
Most of the problems you'd want to avoid could probably be solved if you get rid of the images, and required people to sign up but still post anonymously.
Granted, then it's no longer strictly an anonymous imageboard but in a lot of cases, the images don't add to the discussion anyway.
Well, why do you need anonymity, then? Might as well display names by default.
I disagree with getting rid of the images, though. They are a useful tool, and most forums feature some sort of attachments. attachments that add nothing to the discussion are a culture problem, not a technical one.
I think it's useful to not necessarily have to link your posts to your account if you don't want to.. anonymity from other users and anonymity from the staff have never been the same thing anyway. A lot of the problems on sites like this (HN, reddit) stem from their focus on chasing after and maintaining reputation, which itself can encourage an echo chamber and a sense of elitism. Having an account would make it easier (not necessarily effective, but easier) for the staff to deal with systemic abuses, because you have something more persistent than an IP to deal with.
Anonymity often encourages trolls to come along and inject horrible comments as it is, allowing posting without creating an account would just lower the barrier to such posts - it's not fun for a moderator to have to deal with that (I've dealt with such for about 12 years now).
People are happy to leave horrible comments whether or not they're anonymous, have a pseudonym, or are using their Facebook account.
What's important is if there's an active community encouraging them to do something better. (This is different from just stopping them from doing bad things.)
You could require creating an account and posting through it, but still not show that account to other users. Although then trolls might just create new accounts. It's not an easy problem to solve.
One example off the top of my head: Because some of us would like to put it to productive use and discuss technical work-related stuff without a possibility to link it back to our employer?
I also absolutely love Futaba-style imageboards - it's a great blend of anonymity, simplicity, and community. It's a shame 4chan's reputation is what it is.