I suppose that jump-to-parent-&-back can also be implemented as an extension.

I'm thinking it'd make sense with both highlighting new comments, + a recent comments list.

(If relying only on [highlighting comments posted since the last page load], then sometimes one will miss a few recent comments — because usually one didn't read all comments shown on the page, but the next time the page gets reloaded, [previously shown but not-yet-read comments] will no longer be highlighted.)

I love that extension. However the other day it stopped working for me for some reason and I couldn't figure out why. It's working again though.

Update: and I wish it worked on mobile too.