One reason I'd like the ability to block individuals, and yea even whole threads, is that certain people in here post with deliberatly inflammatory intent. That's ok sometimes, but the problem is that occasionally I actually respond to these people because what they post bugs me that badly. They participate in discussions that are otherwise intelligent, but their inputs are intentionally irritating or distracting and they either shut down the discussion or divert it into flames against themselves. They do it on purpose, but they are usually careful to not break forum rules. Plus I wouldn't necessarily want them banned 'cause, you know, pot, kettle, etc. But it would dramatically increase the signal/noise ratio if I could block a handful of people. It would help me stay on topic as well.
It would lower my blood pressure and reduce the number of times I "contribute" to flamewars if I could simply block their posts. Or threads, now that nuke brings it up. It has nothing to do with "punishing" people, or trying to show them up. Of course, listing the blocked names might make it seem that way, but even that is a form of feedback saying "these people express themselves in a way that I find to be unusually irritating or offensive". I'm not sure why that is considered childish, and how it's somehow better to either keep quiet or continue to propagate flamefests by expressing the exact same sentiment in off-topic post responses.
The above "discussion" between 88 and nuke is a perfect example... Might that have been prevented if one was ignoring the other?