First, I'd like to thank you, David, for giving us the official stance on Parma, though I have to say I found a number of issues with the above statement.
While most magi aren't combatants, those of Houses Flambeau, Tremere, Tytalus, and a great many Bjornear are, pretty much by the definition of the Houses. And I note there still remains an emphasis on the shield grog, which would also go against the statement. Finally, if one browses the spells on will find a great number of combat-oriented magics to be found.
That being said, I can well imagine a great number of Verditius, Criamon, Jerbiton, Bonisagus, and the like would rarely, if ever, engage in combat, but I would hesistate to make any such generalizations about either Merinita or Ex Miscellanea, as they are both rather disparate houses linked only by common style.
My real issue with Parma is that it, combined with so-called Pink Dot magic, would make a number of other spells, particularly of the ReHe and ReTe schools, obsolete. I also find myself wondering that a master would fail to teach pink-dot magic to an apprentice, as it is an easy enough way to render him immune to mundane harm, which would certainly be of great benefit, especially to the aforementioned Flambeau, Tremere, and Tytalus houses.
These are merely personal issues involving a single rule, as any system would have natural exploits built-in. And, despite these issues, I have to say that Ars Magica is by far the most innovative and wondrous game I've ever played (and I've been roleplaying since 1977). I can also appreciate how difficult it must be to have to deal with issues like Parma, as its effect has changed from version to version and a definitive definition has been elusive.
Thanks again,
B