Do you mean that there's some sort of "foul" or penalty for excessive force in fencing?
More fencing links:
http://www.martialtalk.com/forum/showthread.php?t=2605
Sort of... fencers can be given a red card (touch for the opponent) for a "dangerous, violent or vindictive action with the blade, bell guard or pommel" and can be given a black card (disqualification) for a "touch scored with deliberate brutality."
These aren't given out often, and certainly not just for hitting hard. I've only seen the latter once, when one fencer punched another in the back of the head with his bell guard (the part of the weapon that protects the hand; rather large in epee) after a touch. The black card was a no brainer there. Generally, the former is given out when someone is intentionally trying to inflict pain with their touches, not just attacking with poor technique or with bad distance. Neither penalty is a very common one, though I often come home from practices and especially competitions with a bruise here and there, and I've given out more than my fair share.
As a side note, the jacket, knickers and underarm protector are not actually there for padding; this is a fringe benefit. They are actually there to prevent a broken blade from entering a fencer, or at least going very far. When a fencing weapon breaks, the foible (the weak, flexible part towards the end) is usually the part the snaps off, leaving a considerably less bendable, sometimes jagged shiv in a person's hand. If that person is already committed to a deep attack, the momentum can be quite dangerous. Fortunately, high end fencing uniforms are made of different types of ballistic nylon (it used to be Kevlar, but that's very stiff and is not ideal for this sort of impact anyway) and are rigorously tested (or at least, they are supposed to be...)
Unfortunately, the USFA has very low standards for protective gear. Instead of requiring the jackets, underarms and knickers to be tested to resist 800 N impacts and the bib of the mask to withstand 1600, which is the specification required at world cups (certified by the FIE, the international governing body) and by some governing bodies, or 350 N/800 N, which is the basic requirement for the French federation, the FFE (which has been adopted by many others) the USFA only requires that uniforms be made of a "durable, resilient material."
I personally fence in all FIE gear, and would not even think of competing in less than a 350 N kit. The club I coach at does not sell any of the really cheap, unrated uniforms, and I am in full agreement with them on this.