Once you have established that the signaled message is not in fact an error, is it possible to tell code critics not to signal that message for that code in subsequent runs?
Not out of the box. A long time ago I've written an extension that allows to use method-annotations (pragmas) to do that. You can load the code from http://source.lukas-renggli.ch/essential.html. You find minimal documentation on that page as well.
If there is interest, I could include the basic functionality into RB itself. I think that would be much cleaner and easier to use.
Lukas