There is a certain irony in noticing this on a comment I made about the new group chat. On Ivriniel's post I ended up being the highlighted discussion. I have no idea why.
Here's the expanded "All Replies" view for comparison.
I was the first to reply but looking at other posts that is clearly not a hard and fast rule for being highlighted. Ivriniel hadn't replied to me or anyone else at the time and my recommend wasn't from the author either. Yet Kinja's algorithm somehow decided my comment was worthy of highlighting.
Edited to add: Thinking it over, I think the link in the comment to another Kinja post is probably what pushed my comment to be highlighted. But my conclusion below still stands ;)