While looking at the grid I see that Mike posted the last comment. But when I navigate into the topic his post is not visible. I suspect is was deleted and the grid does not account for that. If so that seems kind of weird.
Discussion posts and replies are publicly visible
My reply was under [the first reply under] a legitimately "spam" comment, which was pretty quickly removed after I flagged it. The user account is still there though as of now, which is a little confusing seeing how that account's only 2 comments ever were both spam. I assume the reason it still appears as if I was the most recent poster is something along the lines of, the thread is just hidden but not actually removed in the back-end (but that's purely a guess).