Currently it shows the profile picture of the last person to comment on the thread instead of how (I think) it was before with the profile picture of the original poster. Having the original poster means you can see who's thread it is at a glance which I think is more useful information than the last commenter. It also doesn't repeat the same information you already see with the latest reply. Hovering over the name of the last replier should give their tooltip too.
The change will make it a more efficient use of space as it being repeated is unnecessary redundancy.
