Link is to the tweet that made me aware of the problem. I don’t use the web client anymore (because I can’t forward certain other accounts to it easily), so I didn’t even see it until this showed up on my timeline.
The tl;dr version is that there is a new button in Gmail (temporarily): Send + Mic Drop.
Bright orange, easily visible, what could go wrong?
Apparently there is (was? sometimes? usually? previously?) a different button layout.