That type of syntax doesn't exist, though I agree it would be useful. It would be best if you could submit a feature request here, so our Product Manager can track it as an official request, and reach out to you if necessary.
I put in a feature request for this (for include list, not exclude list) years ago but nothing happened. However, if you pretend that # or similar is a comment character in an include list, a line starting with # will generate a network connection error in the scan and the names not marked will scan normally. Perhaps an exclude list behaves similarly?
I tested this for the exclude, and found that adding a character will cause the list to break off at that point. In the following example"
The first 2 are excluded, but then the third line throws an invalid ip address error. At this point, the list is no longer read, and both 10.25.82.50 and 10.25.82.144 end up being scanned.
It would work for commentary at the end of the list, but not for an inline comment. You could move all commented IPs to the bottom, and that would prevent legitimately excluded IPs from being scanned.
Thank you, but I'm using the list in the reverse... the IPs in the list need to be acknowledged so that they are excluded from scanning. I'm definitely interested in implementing the inline comments.