I've noticed that since a few days (weeks?), the "Show n more comments" link at the bottom of the comment chain does not disappear after clicking. The comments are correctly loaded, the link just doesn't disappear (and upon click, a new network request is initiated again).
This happens on every site in the Stack Exchange network when you're not logged in for the website.
To verify this bug, just open an incognito window and pick a post with lots of comments.