Hello 
I noticed on mobile (Android 10) when I open a usercard and then scroll the page the (backdrop) cloak still there. Earlier it disappeared with usercard when I started to scroll the page. Now it requires an other tap or tapping outside the usercard to dissapears it.
Thanks 
I encountered this slightly annoying issue as well.
This is the annoying part since the overlay prevents us from interacting with the interface and requires us to tap while the card has already been closed.
Replacing mousedown with pointerdown in discourse/frontend/discourse/app/components/card-contents-base.js at d056c1e358d1cb823632aa4a8c51a42e911969b3 · discourse/discourse · GitHub seems to fix the issue.
Those event weren’t compatible with Safari until 2019, so I guess we could use them? Unless there are caveats I’m unaware of.