Interesting find this evening,
I copied a snip of text to use as documentation in my patch and when trying to save the patch I receive the error message;
An error of type type-error occurred: #\" (of type character) is not of type base-char.
I thought, interesting. I went through and started to remove bits of the copied text line by line, saving after each removal to find these two fellows as the culprits
This would be the inverted quotation mark?
Of course, my keyboard would normally just type
" and "
and as such the problem is easily rectified.
Just thought I would share as the only other mention I have seen of a character incompatibility is with non-latin characters.