@rzi I've updated that Gcode section to say that it should be just a single set of parentheses:
Alternatively, comments can be enclosed in a single pair of parentheses, e.g. (comment). Comments cannot include double or nested parentheses, e.g. (comment (a bit more comment)), and they must start and end on the same line.
To be fair, I didn't even realise a comment could be in parentheses!
Ian