The warning category won't exist in 5.8.7 and the modules that use this behavior are the ones that no-one wants to try and debug (including the author, in many cases). So, now we have to test to see if the warning category exists before we disable it?
My criteria for good software:
Does it work?
Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
Comment on Re^7: The trap of reference numification
Okay, so it could go in the 'misc' category. It probably belongs there anyway; there's no point in creating a category for it. And/or do it smarter like Roy suggested.
In any case, it can create nasty bugs, it isn't that commonly used, and a warning probably makes sense.