Actually it can because a nail in the pole can cause the climbing gaff to sheer out of the wood and possible cause a lineman to fall.

Nails sticking out could catch on clothing, climbing belt etc, there are some dangers to doing so, and when I see a sign on a pole that doesn’t belong to the power company I work for... bye bye... it’s gone.

Some drug users stab their used needles in the poles and break them off also. That is a whole different level of danger there.

So ya, it is dangerous in a way but if someone used just a hand stapler it would be too big of a deal. But if you want to hang a sign.... make your own sign holder. LOL.