Dunno, when i used to play with my mate he would run his mic through a bass amp and it was fine as far as i could tell.
Bass Player
itll color your voice but it shouldnt damage anything...id say its fine if your using it thru a cheaper amp like an old peavey...not so much if your playing thru a vintage tube ampeg or something
my old band used to do it. i think it was a peavy, but im not sure. it worked fine

BC Rich Warlock
Dean 88
ME682-In Progress
Carvin SX300
Clayton 1.0mm picks
Planet Waves cables.
my band does that now through a huge hartke amp and it works just fine