At least on 4chan, the content is all time-limited, so finding persistent examples isn't really doable. However, the more niche boards are full of quality content for their particular niches, and depending on the culture of the particular board people can be very helpful.
I personally appreciate 4chan for generally weighing the value of a particular post on its own merits rather than any sort of user history or whatever - it's a good counter-balance to places like HN or Reddit where comments can get buried or removed if they go against the hive mind and there's no post history to dig through. I definitely get how the trade-off of inflammatory posts being more common isn't as palatable to some people, though, so it's kind of a mixed bag on if you'll get anything out of it or not. Opinions, etc.
The inflammatory nature of the chans is in and of itself a filter - people that partake in imageboard discussions tend to be more thick-skinned as a result.
I personally appreciate 4chan for generally weighing the value of a particular post on its own merits rather than any sort of user history or whatever - it's a good counter-balance to places like HN or Reddit where comments can get buried or removed if they go against the hive mind and there's no post history to dig through. I definitely get how the trade-off of inflammatory posts being more common isn't as palatable to some people, though, so it's kind of a mixed bag on if you'll get anything out of it or not. Opinions, etc.