Okay, I'm embarassed to say I tried the one-handed action rack a few times after seeing Terminator 2.
I'm only guessing, but I'd say it's not particularly harmful. When I shoot practice drills, I rack the action very
hard and very
fast. After all, that's what I'll be doing on a Really Bad Day, and I'd have to believe that a gun like the Mossberg is made to be racked hard and fast.
As for practical applications of the Linda Hamilton Technique, I guess if one hand is injured in a gun fight, it might be useful, sorta. But shooting the gun once you've chambered a round that way, well...