I'm always reluctant to put phantom on (most cheap desks have global phantom not channel-by-channel) unless I have a complete rack of condenser mics (which has never happened).

There are two issues hiding here.

First, if I get forgetful and senile and put a jack-socket-to-cannon up in the stage box and forget to put the other way round adaptor on the other end at the desk and put it in the line in - I'm going to fry something.   

Second - I just don't like the idea of putting phantom up on a dynamic mic.   MIGHT it alter mic characteristics? I ask because we were performing (but not desk driving) recently and the mics - mostly SM58s but a few Beta 87s (which is how I know that global phantom (it was a Behringer desk) was on) - we were singing on the SM58s - seemed to be a bit "on or off". Normally it's easy-ish to listen to yourself in the backwash of the FoH speakers - or in the foldback if it's any good - and fade your own vox in or out to get the precise balance you want as the song varies, by backing off the mic a spot. This time it wasn't. Either one was there (and a bit too much there) or one vanished.

Foldback as such was not audible but might have been contributing slightly.

Views? COULD putting phantom onto an SM58 change its behaviour?