Though it was a few years ago, as someone who has worked the polls, here is what I recall about the poll operation and ballot collecting process:

In MA, absentee/early ballots are sent out with barcodes that can be mapped back to a central DB. Afaik a maximum of one early ballot is sent out to any given voter. If you lose it, you’re walking to your polling station on election day. The mailed/dropped off ballots are scanned so that they’re routed to the correct voting precinct; they’re given to us on Election Day to run through with the in-person ballots.

On Election Day, we sit there with registered voter lists (the list is sharded, not duplicated - i.e. someone works a-f, someone else works g-k, etc.); people come in, tell us who they are (no, no id is checked, but they do need to give us a full, correct address that matches their stated name); they are marked off as “voted” on the list. Voters are provided with a ballot once they have been found on the list and marked off.

Absentee ballots are run through the machines throughout the day; for every single ballot, we match it to a name on the list, and . If there are any duplicate ballots, that is caught at the voter list checking phase, and is flagged thusly for any necessary follow-up (confirmation, disambiguation, or legal action as necessary) and the extra ballot is set aside (whichever one we come across second).

I’m pretty sure we had zero duplicates when I did it in the 2020 presidential (I feel like I would have remembered that, considering the political context at the time), and iirc we processed something in the neighborhood of 10,000ish ballots.

Which is a joke anyway. Signature verification is something that should be abandoned. People don’t care about their signature anymore. Plus, do the people doing the verification get any sort of training at all? Has there ever even been a study to show how accurate such comparisons are?