I don’t know, there seem to be various levels of anonymity with different social implications. Let’s roughly differenciate between:
1. Full Anonymity (no way to differenciate between user A and B except by the content)
2. Anonymous Pseudonymity (Users can take usernames, but they don’t mean a lot because they can be changed fast and there is no per user post history)
3. Accountbuilding Pseudonymity (Users usually stick to their accounts, Per user post history or karma is visible and meaningful)
4. Mandatory Real Names (on top of the stuff in point 3 you also have to use your real name - but face no consequences if you make something up)
5. Enforced Real Names (same as point 4, but the service provider has to check your identity)
Positive effects of mandatory real name policies could never been proven — as far as I know they haven’t improved civility e.g. on facebook.
I believe the secret lies more in the feedback systems and how easy it is to flip or flop your position away from what you historically said. It helps if all community interactions or rules are clear and minimalistic instead of arbitrary and arcane.
All of this together weakens or strengthens the impact of the kind of user you mentioned. So in short: the emergent culture on really bad image boards is also part of their systemic design, just like it is with hn, facebook, instagram and any other online plattform. I think the type mentioned in point 3 (accountbuilding) paired with clever measures to keep the aims of the community aligned help a lot.