I think it might actually be a good idea to give any poster the power to delete replies in their post's comments thread - Facebook does this automatically and I don't think it's a problem in real life, except of course for the trolls themselves - but that would require development resources, and as ever, we have none.

This is a terrible idea. People already try to bully people out of disagreement with their point. Giving everyone the power to delete dissenters in their threads introduces drastically undesirable incentives. It means that people would, and, indeed should systematically downvote every comment in a thread if they believe the local PostDictator has or will abuse their local dictatorial powers. That is the only way to eliminate the bias in the conversation.