I think it depends on motive, or reasoning behind letting someone know that you have killed or injured greatly another.
But if we are talking about a personal bio, especially one that is intended to boost ones credentials, I think that detailing kills or violent encounters is wrong.
The reason is simple. We try to better ourselves as martial artists because we want to be better combatants, as well as better people. By saying "I've been in this many fights" or "I have killed before..." as a means to define credability, then what you are essentially saying to those who are also trying to better themselves is that getting into fights or killing makes you more credible. Those who do this are in a sense condoning and promoting violence, because others who look up to such individuals will seek the same experiences so that they can gain similar credibility.
If you are a true warrior, and you choose to take a profession that involves killing another; or if you are a privite citizen and are forced to hurt or kill another in defense, your motives should not be to gain credibility either before or after the fact. If you are willing to hurt someone else for credibility, even as an added 'perk,' then you are morally corrupt, a poor role model, and not much better then street scum or terrorists.
It is O.K. to divulge information about a violent past if there is a lesson or a altruistic benefit involved. But to divulge such information for the sole sake of marketing or resume building is morally currupt and not the measures of a true warrior.
Such people who do those things need to re-evaluate their angle in the combatives world, because such moral corruption one does not belong.
