Don't forget that many documents such as furloughs, paroles, oaths of allegiance, etc., were produced in duplicates with one copy given to the soldier.
These were obviously folded and over time subject to deterioration.
Looking at those captured in the CSRs, which were kept with Union records, it is often difficult to read name, rank, and unit/company designations. Also, many have blotched areas and holes due to the folding process and paper disintegration.
Verbal misunderstandings need also be considered as well as senility on the part of the veteran.
I agree that stone cutters take their part, I have an uncle buried in 1908 and then a grandfather who have their given names misspelled on their stones!