This is an admittedly small thing, but when using Gmail in Firefox, the mouse pointer does not always change to the pointer finger when navigating the message list. When viewing a message and returning to the inbox (or whatever mail folder/label you are in), the mouse cursor will remain the standard arrow cursor. If you move the mouse out of the message list and over to the labels column and back, it will change back to the finger pointer cursor.
It's really just a cosmetic thing, but the cursor style always works when using a Chromium browser or Safari on macOS.
