Does bleeding damage stack?
Solution 1:
Bleed damage does not stack.
Confirmed via testing as of 12/20/10.
If someone is hit once with a bleeding weapon, they sustain initial damage and then bleed for the specified amount of time (for example, six seconds for the Tribalman's Shiv). If they are struck again with that weapon, they sustain initial damage again, and the bleed counter resets.
Solution 2:
I would suggest it is likely to be that the bleed damage is sustained by additional hits, but not increased. I think it is the same for fire damage. Time to get out a Kukri and prove it though..