Hmmm....Silver and his opinions about the rapier always opens a can of worms.
None of the Italian masters tell you not to use additional techniques (hand grabs, etc.), except that they note that the offhand is rather easy to deceive (so using the hand is good when done correctly, but "hunting" for your opponent's sword is generally a bad idea, not for etiquette reasons, but for reasons of your own safety). In fact, Fabris details a nice technique (the volta di pomo) for using the pommel to strike your opponent.
As to the lack of defensive capability, I have not found this to be true, but as I'm not one of the masters, my findings mean relatively little. However, Fabris, Capo Ferro, et. al. seem to feel that the rapier is quite effective for defense
provided you don't forget the fundamentals of rapier theory.
Ahh, the lateral movement argument. Now leaving the Spanish school aside (as I know next to nothing about it) and speaking only from the Italian point of view. Why would rapier be linear? Because linear movement is all you need. You'll notice that none of the techniques of Fabris, Capo Ferro, Giganti, or Alfieri are non-linear (not including the volta/girata, but I'll get to that). After all, what does circling your opponent give you? You merely give him a nice tempo to utilize against you. Ahhh, but you say, "what about the volta/girata?" Well, true, you do take your body off the line of the attack, but you leave your rapier on the line of attack. Thus the girata doesn't make the Italian Rapier non-linear any more than the inquartata makes sport fencing non-linear (of course we can quibble and say anything off the line is non-linear, but I'm looking at the Italian style of thrusting directly at your opponent, as opposed to the Spanish style of "spiralling inward").
One thing I've noticed, is that the rapier masters include the recovery as part of the technique (usually something like: "...ritirarsi con Prestezza in dietro fuori di misura in Guardia.") so they understood that a successful attack does not end danger. In fact, Fabris specifically includes the recovery (safely in guard) as part of the correct execution of a lunge.
Now as to Silver disliking rapier. Well, the rapier vs. shortsword argument won't be settled for a long time (if ever), but I think it really boils down to the battle between long and short. Each has its advantages and disadvatages, given the specific tactical situation. Generally, every argument I've seen between pro-shortsword and pro-rapier has always ended up being a matter of exchanging counter-techniques for given scenarios with no end in sight (with no "ultimate victory").
Steve
I have no experience with either sport or WMA rapier (just trying to figure out the longsword at the moment) but I am now reading George Silver and I find it interesting that he has several points which bear on this discussion.
1. He seems to be quite critical of "limited" rapier fencing which restrict the use of grabs, hand strikes, blade grabs, foot sweeps and the like. I get the impression that modern sport rapier work has similar restrictions.
2. He seems to suggest that the problem with the rapier is not its lack of offensive capacity, but rather its lack of defensive utility.
3. Regarding the "rib breaking" thing, Silver seems to suggest that even rapier thrusts that are lethal after the fight, don't prevent the guy from killing you and then expiring later on.
Any one with a better understanding of Silver, please feel free to correct me on these items.
I also have a question. In sport fencing, is it permitted to do lateral movement (if so, how much?) or is it only backwards and forwards? A 2 meter wide strip (is this correct?) doesn't seem to allow much space for lateral movement.