I just recently noticed the following button in the comment section:
Clicking it appears to make the comments look somewhat like what you see on Mastodon, but I'm a little unsure about it's exact format. Is it only showing parent comments? Is it showing parent and child comments all mixed together? If so, in what order? Is it in order of when the comment was added? If it does show child comments, is it possible to see that child's context?
I believe the idea is that it's a way of ensuring that you see all of the new content. As it is, sorting just by new alone doesn't always work, because a new reply to an old comment doesn't filter to the top that way.