Usually any mic you buy has a + and a - wire inside, and both are isolated from the ground connection (chassis). All have their own pin in the XLR receptacle, so +, - and GND. That is what's considered a 'balanced mic' in the above statement.
Some older mics, particularly notorious are old ribbon mics, do not have a separate ground connection, but have ground and minus together. If that is the case, this will short your phantom power supply. This power supply could be damaged, burned out - or it will have provisions against damage, but then still such a mic will be responsible for removing the phantom power for all other connected mics.
The first paragraph is not wrong in saying it's better to leave phantom power off if not needed, but generally speaking, a mic (and mic lead) that doesn't need phantom power but is wired the right way will have or cause no issues whatsoever. I'd say 99.5% of mics today are in that category.