My idea is that if you ping during the first turn of matchmaking (no one has moved yet) you can reconnect within a certain duration like 1 minute before you get a point penalty.

good suggestion for everyone who have bad internet like me.

i support this

Also it could display a message on the opponents screen like " Waiting for ___ to join back... " and have a countdown timer

Maybe OPs should be able to lengthen the time to wait for more.

There are no OPs in a matchmaking server..? Or maybe I misread what you just said

Oh no, It's me who misread the original post.
I mean even for normal servers like sparring etc.
It'd be nice to be able to wait for the other player to come back.