General Discussion
In reply to the discussion: A Warning For Voting Day [View all]Ms. Toad
(38,634 posts)(A Republican county, a mixed county, and a Democratic county) are required to pair election workers (One Republican, one Democrat) working side by side precisely to prevent monkey business. And Democratic observers are trained to watch for a single worker interacting with a voter in any circumstance in which the worker can see the ballot, as well as anything a worker could do that would invalidate a ballot.
That said, none of the election workers I have ever interacted with (the three counties in Ohio (the Boards, higher up workers, as well as workers hired for election day) or the higher up officials in counties/states across the country) have ever had any interest other than running a fair election.
As to the specific comment, once a ballot is read it can't be unread - there is no way to separate the ballot after the fact. A mark on the ballot would only invalidate it if it is made in the area of the timing marks or the voting area. Both would cause the machine to reject the ballot and require either an override (if marked in the voting area and it resulted in an overvote) or would require a new ballot (if the marks were in the timing area, causing the ballot to be unreadable entirely).
So it's good to pay attention - always. That's why the Democrats have had observers in as many counties as we can place them. But this specific concern is not (as stated) a concern beyond checking to make sure your ballot is actually read (and you don't override an error message unless you deliberately over- or under-voted).