One thing I still find very frustrating with #fediverse is the way interactions often are hidden. I commented on a post, it looked like I was the only one, but after opening "original post" I saw several other comments that were invisible to me at first.
This feature means I miss out on interesting conversations and makes it more difficult to find new accounts to follow. And I just don't understand why this is.
As far as I can tell, that's the expected behavior of the Mastodon UI, and we're supposed to open the original post if we want to see those conversations.
I believe the idea is to filter out all of the other comments by default to focus on our own exchanges.
Are those the comments that also replied to the same comment that you're either looking at or that you've replied to?
My impression (I could be wrong) is that Mastodon treats it like a tree of branching threads, so it will display comments that are on the same fork of conversation that you're on.
So that if you click on the first post, THEN you're looking at the whole tree, and it will show a lot more comments.