@feditips
I've been trying to reproduce this; it doesn't happen every time.
It only seems to happen when new material appears at the top of the feed while I'm clicked down into a post.
And it doesn't go all the way up to the top, unless I was near the top to begin with. Maybe it is moving up the feed the same distance as the amount of new material that was added to the top.
I think this might be why Twitter changed to make you click to see new tweets at the top of the feed.