"In order of grid entries, the 33 misprints lead to further thematic material."
This should actually read "In normal clue order", i.e across clues, then down clues. "Grid entry order" would be 1ac, 1dn, 2dn, 3dn, 4dn, 5ac, etc.
In one respect the misprints are really necessary for the solution, because what they reveal shifts the focus of the puzzle. The preamble alone is not clear enough for a correct solution because of the ambiguity of two referents. I made the same error as Williamseal until a friend put me right. Had I taken the trouble to go through all the misprints in normal clue order I might have avoided that initial error.
I trust that the following doesn't reveal anything not already known.
Two reasons why I think the 33 misprint thematic material is worth going through - it leads to the 'hiding in plain sight' element of the puzzle that surely really is very well constructed; and it reminds the solver of the pseudonym [letter][digit][digit].
That the occupant of the thematic cell historically is represented by the occupant of the same cell's identity in the other sense of the term was very satisfying, to this solver at least.
Have completed the grid and the change / highlighting, but am struggling a bit with the second message. What I have for the message would possibly work if the misprint in 35a was a 'b', but I have it as a 'd'. Is d correct?