Everyone having the power to curate their own filter bubble is actually the only way to defend against people trying to shape public opinion IMHO.

X has a similar feature. It just reveals a "show hidden" button if there's hidden replies, and people can view and reply to them anyway. I've seen shockingly little hiding of opinion and it mostly being used for spam and nsfw content.

If this was commonplace everybody would know it happens, so they could defend against it by using their own relay lists in order to read comments against the authors who heavily censored their own reply sections. The concept of a single reply section should cease to exist anyway, there should be a ...

this is correct if the client only reads from the author's relays, it should pull from other relays to prevent the author from controlling what you see, but then also you will never know where these comments are.