[yoklov]

I think this is mainly an issue on macOS if you use a vertical sidebar, having to do with supporting it's translucency.

I think there's away to turn this off too, but I don't remember how, sorry.

[lordnacho]

Where did you hear about the translucency hint?

https://xkcd.com/979/

Not trying to turn HN into a bug hunting board, but I found this:

https://bugzilla.mozilla.org/show_bug.cgi?id=1404042

Might be useful to someone.