So, I decided to view the source code of this Homestuck personality test and saw the following:
"Little is known about the Blood aspect, other than at least one Blood player used his blood as a bonding point, and (through a combination of anger and empathy) tried to hold his failing team together. As such, Blood could be tied to emotion or kinship.
The Blood player held together his team. Karkat clotted.
…That sounded a lot more profound in my head. :P