Signature standards

The Star-Tribune of Minneapolis-St. Paul analyzed 2700 rejected absentee ballots and found that a third of them were rejected due to signature problems. That's not exactly an objective criterion (say, the deadline for arrival or the requirement to have a witness). Most of these badly signed ballots are probably legitimate votes from legitimate voters whose signatures are simply variable.

The question: What appeal if any is available to overrule the opinion of the amateur graphologists in election offices?