If you all visit a user profile, you'll now find all the way at the bottom, a category called "References (Optional)". There are two text boxes there for you to enter names of references.
The description reads:
I'm going to be straight-forward with all of you. We have some disgruntled former users here that keep reregistering on the AC and their apparent intent is to cause acrimony here - particularly in the buy/sell/trade area. They have a long history on the NSSA boards and cwreenactors of not making good on their sales.Primarily for buyers and sellers. Tell us the names of some folks in the hobby who KNOW you and can verify that you are who you say you are - preferably folks who are already members in good standing here on the AC.
This reference area, editable in your User CP is NOT mandatory. But I suggest you use it, and I suggest you request sellers who you are conducting a transaction with and who you are unfamiliar with to use it.