Okay, the sliding avatar thing just started working for me (I didn’t or do anything), it seems to be hit or miss if actually happens, but at least I know what people are talking about now. Also the entire post jumping back and forth stopped.
However, know there’s a big chunk of wasted real estate in the column that all the avatars are in since the space is needed for them to slide around. Not a big deal, just different.
This all sort of reminds me of when vB switched from user names/stats between each post to being to the left of each one with people passionately arguing about why one was better than the other.