Well, this was an interesting and elightening article on how damaged a sword could get in battle.
However, in response to the discussion, I feel compelled to quote some passages from the Goliath fechtbuch, as translated by Mike Rasmusson at
www.schielhau.org, wherein the author of the fechtbuch repeatedly instructs to displace with the long and short edges.
"When you stand against him in the guard of the roof then strike high to his head, if he then springs from the strike and means to come forward with a traversing (zwerchau) strike by striking to the left side of your head, then let your sword's long edge fall on his sword, if he then strikes across over to the other side, just then strike your sword ahead traversing under his sword to his throat so that he cuts himself with your sword."
"Counter against the Lower Thwart Strike
When he strikes you with a Thwart from his right side high to your head's left, then displace with the long edge and stay with the point in front of the chest, if he then strikes from the sword over with a traverse to your lower right opening, then you also strike a traverse through low between you and also to his right side, and bind thus on his sword and stab just then to his lower opening."
(Note that the second action is low zwerch against a low zwerch, an action which just can't be anything but edge to edge, which essentially makes a parry followed by a thrust)
"if he stands against you as if he would stab: put your left foot forward and stand against him in the guard of the Plough on your right side and give an opening with your left side, if he stabs to that opening then wind the sword onto his stab to your left side with the short edge on his sword, setting it aside, and stride then with your right foot and stab him Just Then to his face or chest."
"How you drive the the first two windings from the Ox only on the right side is thus: When you come to him in pre-fencing, then stand with the left foot forward and hold your sword before your head to your right side in the Ox. If he strikes one high to you from his right side, then wind the short edge on his sword to your left side in his strike into the Ox and stab"
"When you come to him with pre-fencing then stand in the guard of the Ox on the left side, if he strikes one high to you from his left side then wind against his strike with the long edge to your right side on his sword and stab him one high to his face, this is one winding. If he displaces the stab and punches the sword to the side, then stay on the sword and wind the long edge to your left side into the Ox on his sword and stab him one high to the face. These are the four windings from the two upper hangings on the left and right side."
It also seems the only time Silver tells you what part of the sword to use in parrying, it's the back/false edge and the true edge.
"24. If at sword & dagger or buckler he strikes in at the outside of your right leg ward it with the back of your sword, carrying your point down, bewaring you knuckles downward & your nails upward, bearing your sword out strongly towards your right side, upon which ward, you may strike him on the outside of the left leg, or thrust him in the thigh or belly.
25. The like may you do if he strike at your other side, if you ward his blow with the edge of your sword your hand and knuckles as aforesaid, casting out his sword blade towards your left side, this may be used at short or long sword fight."
Now, understand me here. I'm not saying flat parrys aren't used-there's good evidence of them too. Nor am I saying use your sword in the manner of Hollywood heros-no credible person in the Medieval sword community does. And no one can accuse me of being "emotionally attached" to edge parries-My first longsword text was Medieval Swordsmanship, I practice flat parries, and have argued vociferously in the past that they are valid for European swordsmanship. But I'm also a man who can be swayed by evidence, and I can't think of better evidence than the plain words of the historical masters. Disagree with them if you will, but to deny what they set down in plain writing reveals an "emotional attachment" of it's own and is not really worthy of a swordsman.
"Beat the plowshares back into swords. The other was a maiden aunt's dream"-Robert Heinlein.