Some when they talk about concussion discuss it as if it is just a simple hit to the head which they can recover from easily and everything is fine. It is just a little smack to the head, they can continue, no worries. The thing is that this is not the case at all. Concussion is no joke and is something that needs to be taken seriously, very seriously.
I have produced a discussion on the subject of concussion, why it needs attention and some of the very important aspects pertaining to it. This can be found here: http://www.academia.edu/37041914/Concussion.pdf, or I can be contacted for a copy of the same document. This is a subject close to me as I have received quite a few concussions and know that they can have a debilitating effect on your life.
The above change needs to be made at a community level, simply that people who strike to hard need to be told that they are hitting too hard and that they need to stop. A community can simply refuse to engage with such people as a sign of support for such a move also. At a policy level, organisations can stipulate the levels of impact allowable and permitted in competitions. If there are no such organisations, event organisers can achieve the same by stipulating the same in their rules for competitions.
Some will suggest target restriction. This does not prevent the area from being struck, it just means that the it gets struck unintentionally, or gets placed in the way "gaming" the rules. In sport fencing, in foil, the head is off target, but it does not prevent them from wearing masks to protect against the blades which manage to go in that direction.
The greatest argument will be for increasing protective equipment, and for some this will be the first place where they go. It is the easiest thing to change, but it is a patch job and can lead to worse situations. Personal Protective Equipment (PPE) is the least effective method for reducing risk of injury. Often an increase in PPE can lead people into more risk taking situations thus reducing or neutralising the effectiveness of the PPE. Larger helmets make for larger targets, and also can lead to whiplash injuries. There is also the brutish mentality of some who think that because a person is wearing extra gear they can hit them harder.
People simply need to stop hitting so hard. Officials need to enforce rules of play which discourage hard hitting and enforce them strongly. Clubs also need to create a culture where hard hitting is also discouraged. If you have people in your club who are hitting hard and you do not feel safe, talk to them. If this comes to nothing, talk to the head instructor. If this comes to nothing, leave. Only when people use the power that they have will an impact be noticed. Remember, this is your safety we are talking about.