I would say that, at its best, imageboards create a Darwinian survival of the fittest regarding ideas, while stripping away any sort of ethos that would taint someone's opinion of the idea being shared. The problem with this is the same one plaguing /pol/ right now, a group creating mob rule and a hugbox. The problem is the concept I mentioned is a commonly shared one, and the mob uses social pressuring to chase out rival groups, while convincing themselves that their success is this concept working, despite them using identity politics to undermine the concept.
At its worst, imageboards become just like a subreddit. Wrongthink threads get met with sagebombs and cries of "bait" and "shill," moderation works to maintain an ideological consensus through direct action hotpocketry, and commonly-held beliefs go completely unchallenged and become "truths," despite evidence to the contrary existing. After all, if a tree falls in a forest, everyone says they didn't hear it, and those that did are pressured into denying it, it really doesn't matter if it made a sound, now, does it?
In the end, like all things social, it comes down to the integrity of the community in question.