sure, but he asked if he could use Auto Bracket in M.
It all depends on what you're shooting, some people almost never use M, some people only use M. I know personally I use Av 95% of the time.
Yes you can but its a bad idea to auto bracket for anything at night. The timer tops out at 30 sec and often at night that is not enough for a +1 or +2. I learned this the hard way last year when i returned home from my trip. My normal shot may have been 20 sec and my +1 or +2 are at 30 sec which is not even close to a correct +1 or +2