No, I've never dealt with Comcasthawk or you before, so I cannot speak from experience here.
There's no set number of non-paying strikes, and there's also no way of getting booted off of the boards from being a poor buyer/seller. The Forum Sales area is supposed to be self-policed by its members and the mods generally try to stay away from disagreements here. This thread was created to allow other members to see which people to avoid buying and selling from. I can't stop you from making transactions with anyone on the Probation List, but the general idea is to stay away from those "problem members" until they clear up the mess that got them there in the first place. If someone on that list wants to get off it, he/she must make good on the transaction, or have the original finger-pointer forgive them and make a post to have them removed.
That's my interpretation, anyway.
Andy