I didn’t, I just noticed that 3 hour-old comments were highlighted, while 4 hour-old comments weren’t (but I just saw a highlighted 4 hour-old comment and an unhighlighted 3 hour-old comment, so it might be something else).

Update: the limit seems to be 4 hours for comments, not 10 minutes.

I just entered the thread, so in that case all the comments should be highlighted.

I didn’t follow any links.