I'm currently running in a situation where I don't know why someone else added a specific visibility condition.
Therefor I think it would be great to have the option to add comments or documentation to visibility conditions.
Or does someone has an alternative to keep track of why a visibility condition is added?
Indeed a useful addition, I proposed the same idea some time ago ('Add developer comments / annotations in Pages').
You could also use a text with a 'hidden' class added to it, but although not visible on screen it will be in the html source code.
Lets hope that it will part of the modeler itself in one of the upcoming releases, f.e. with the option for modelers to hide/show comments and also avoid that it will be in the actual published html.