I assume you are referring to the files list you pass into xrun with -f/-F option. Yes, you can add comments with "//" notation at any point in the line and the remainder of the line will be ignored.
yes, I'm referring to the files list, which is passed to xrun command with the -f/-F option.
@tpylant, thanks to your comment!
BTW, is there a difference between -f and -F switches?