I'm going to read up a bit on trust systems tomorrow and see how this might be doable in an anonymous way.
"Anonymous" would not be the correct term. You'd rather talk about "pseudonymous" credit system.
Your pseudonym would be your GnuPG ID.
In an anonymous network, all nodes are equivalent and you can't tell them apart. In a pseudonymous network, they are not, but you just don't know anything about them except their ID, which can be as meaningless as a random number.
Meh, sounds like a load of pedantry to me. Heh heh. I guess it's good to know specific labels every now and then but in the end it's best to just take the message for what is if you understand it.