I'd love to hear if they made any progress in tracking down the 'interesting WebRender bug' from https://news.ycombinator.com/item?id=22359574
I think it's tracked under https://bugzilla.mozilla.org/show_bug.cgi?id=1604492 It's still open, but it seems people haven't been able to hit the bug on the last few nightlies (this is also my experience), so it's possible the bug was quietly fixed as a side effect of some other patch.
Programming can be so hard: "So then what was the bug?"