There are several different x10 (+20dB) XLR in-line signal boosters available that require phantom power to operate and not pass it on to the input connector. I don't know of anything that is just a PP guard device.
This is a general rule, but there are exceptions for certain makes of ribbon microphones. The phantom-power short-circuit fault current is limited to about 14mA so as not to burn out a coil, but it can do irreparable damage to the suspension of a ribbon microphone, so the general advice is not to use ribbon microphones in a phantom-power environment in case a fault is present or develops. Only if the microphone is not wired in this way, or if there is a fault in the cable or connectors will the coil see any of the 48V phantom power. Provided a dynamic microphone has its coil floating with respect to its case, it should not be worried by the coil being up at 48V, and the differential voltage developed by the coil across the two internal cable conductors due to varying sound pressure at the diaphragm will be passed on to the pre-amplifier as expected. The +48V phantom power is supplied as a common-mode voltage on the two internal conductors of a microphone cable referred to the outer screen (0V).
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