What do you mean by them being hidden? Do you mean that only the thread titles are visible by default? Until there are more than 5 comments, you can see everything in-page, without navigating away.

Yes, the fact that I see a title that may be carefully considered or automatically generated for what may be some comment that contains 1000 characters or simply 10 more than the title is disconcerting. Scrolling is so much faster than aiming and clicking on a button to open something that is hidden. I mean how much screen real estate needs to be spent to save a little screen real estate? How many things need to be considered to read all the details. I consider it bad form to reply to a question or any social media post if I have not read all or at least the first 20 replies, answers, comments before I open my mouth. This is why I came to the post. Either to learn something, to see what others have answered or to offer my knowledge. Having to navigate to do the default act of reading the information is absurd.

It's a balance. When there are lots of comments, we've seen that some people won't keep scrolling to get to the actual answers. (We saw that on SE, and it's clear from the amount of repetition on some other platforms that it's happening elsewhere too.) Maybe we need to add an "expand all" control for people who want to see everything in all threads. (Someone did start work on "expand whole thread" so you could see that 27-comment thread in-page instead of having to navigate away, but the change hit a roadblock and we need to sort that out.)