https://bugzilla.mozilla.org/show_bug.cgi?id=1867975

I filed a bug report some months ago for that very thing, except I expressed it a little differently.

You'd think someone would want to fix it. It's one of those little things that can escape notice, still it is clearly a mistake.

It is still relatively early days yet and If I understand the underlying problem, it is one that the scrollbar is no longer a part of the mail list component, so a fix will probably require some serious refactoring. Small, annoying and I would guess the result of someone taking an expedient route to delivering a release instead of mastering the entire component they were replacing. I would expect the "fix" to be slow coming.

I suppose it's enough if the devs are made aware of it. Hardly a big deal in practice. Thanks Matt.