I think he was implying that opening a knife hard is essentially an "impact" in and of itself. The manix should be able to handle a lot of opening and closing without any issue or damage....WITHIN REASON. if you are opening and closing it hundreds of times a day then yeah, metal parts will eventually wear. Also, I think what Rasco said has a lot of merit. To open the knife with a flick of the thumb creates a bit of an impact. To open with an extravagant flick of the wrist creates a much greater impact (and looks pretty ridiculous anyway IMO).
The manix is a very well built knife and if you choose to flick it open in a sane and controlled manner I can't see it being too big of a problem...even if you do it a little more than is absolutely necessary. If opening and closing your spyderco more than is absolutely necessary did damage then most of us would be in trouble.