Notes:

I'm not sure if this qualifies, since this was something that happened to what looked like the old UI. Frankly, I don't know if it was a different new UI or the comments backend being changed and it affecting the old.
Context:
On the Nacy Mace Transgender Bill entry (an awful thing to read), the comments section looked strange despite the UI looking like the old UI based on the top bar. First off, the formatting of the profile name and time is very close together, making the size of them look disjointed. Secondly, and most importantly, I couldn't vote on a comment, despite being logged in. Finally, the top comments weren't visible despite there being more than 30 comments (when the Comment UI mysteriously reverted when a new comment was made, there still wasn't a Top Comments section, so I don't know the criteria for that or if the criteria were changed).
The old comments UI was provided for context using this very entry.