PA voter here.
Several points:
My handwriting is so atrocious that my scribbled date on the exterior ballot is illegible anyway. I’ve been voting by mail (I hand deliver the ballot days / weeks before the election to my local library) and my votes have always counted. The exterior date is irrelevant, as the instructions state clearly that the ballot must be “received” by County Voter Services by 8:00PM on election day.
It is against PA law for me (or vice-versa) to deliver my spouse’s sealed ballot to County Voter Services or my local ballot drop-off location, unless she was fully disabled and can’t drive, etc. I guess this is PA Republicans’ effort to stop “ballot harvesting” or whatever it is called. A valid ballot is a valid ballot, no matter how it is delivered to Voter Services, so another Republican attempt at voter suppression.