Scrolling is slow and laggy on topic pages, but quick and responsive on other pages on the site. It may have something to do with the topic-timeline widget.
Seems just fine for me can you show us? I’m trying to replicate
It seems proportionally worse the longer the thread. Try this one. Scrolling with the mouse wheel is perceptibly laggy for me.
Well, now it seems to have fixed itself. 
Are you using chrome?
fine for me…
Windows 7, Chrome