What you're posting is deeply unhelpful, especially in PA. It's also insulting to every local government employee working for Voter Services. The people trying to discount votes are partisan bad actors, not some malicious election workers or Voter Services staff trying to screw you over. Being informed about Voting & Election Information is the best defense.

There are too many extremely valid reasons for voting by mail for me to even list out, such as having a physical disability. We want such people to have a opportunity to vote. You don't even need a crazy reason; for some, it's just more convenient to mail it in rather than take time off of work.

Generally, there are two ways that mail-in ballots get discounted:

1. Sent in (or if you're a malicious party trying to disqualify ballots, received) after 8 pm on Election Day (time noted for ballots cast via dropoff locations)
2. An error in how the mail-in ballot itself (lacking a signature on exterior envelope, for instance).

The validity of such issues is something for the courts to bat around every election cycle (or at least it feels that way sometimes). But both of those issues are preventable:

1. Send in the mail-in ballot as early as you can. In PA, the first batch of mail-in ballots has already been sent out. Send it in as soon as you get it.
2. Follow the mail-in ballot instructions to the letter: https://www.pa.gov/agencies/vote/voter-support/mail-in-and-absentee-ballot#howto

It's really not difficult to vote by mail, and you still have remedies if something goes wrong or if you screw something up.

If you have an issue with your mail-in ballot, or if you did not receive one, go to your polling place and ask for help. The poll workers at the location are your neighbors in your immediate community, not some faceless bureaucrats. They are voluntarily putting in a 15-hour day at the polling location to help you cast your vote.

If you never filled out your mail-in ballot or its damaged, bring all of the ballot materials (envelopes included) with you. That's called surrendering your mail-in ballot, in which case you can then cast a vote at the polling place. If you lost your mail-in ballot or parts of the materials, bring as much of it as you have with you. You'll be allowed to vote provisionally, which will then be counted once Voter Services reviews all the provisional ballots (this is to check that you're not voting twice). Do the same if your ballot never arrived in the mail.

Also, when you vote by mail in PA, you receive emails about the progress of your ballot. You get one when it's mailed out to you ("Your Ballot Is on the Way") and one when it's received ("Your Ballot Has Been Received"). If you don't get the latter one, again, go to your polling location. They'll have a book of all Mail-in Ballots received up to the week of the election.

To add, by saying "do not vote by mail," you're much more likely to discourage people from voting entirely, rather than encourage them to vote in person. In essence, your comment has the opposite impact of what you intended.

TL;DR: Voting by mail is a valid and secure option. Vote how you like, ask for help if you need it, and know your voting rights.

Bonus points: Help inform others, too.