A dead battery will damage an alternator as will a battery with a bad
cell.
It is a matter of time and chance when and how hot the alternator,
regulator, or rectifier get and when they will fail.

"An alternator was never designed to charge a completely dead battery"
http://www.stretcher.com/stories/02/02jun17h.cfm

A discharged, but not dead, battery is ok to jump start and allow the
alternator to charge it up. A discharged battery will read around
11-12 volts unloaded or minimal load, 100mA. 8 volts on the battery
indicated that it was in a deep discharge state, not good.

Unless it was a nearly new battery, I would do one of two things if it
does charge and start the car:
1. Get it load tested on the coldest day in the near future, replace if
it is marginal.
2. Simply replace the battery with a new one for the peace of mind.