Sorry, not your mate Bob
Also, youre inferring things that are not implied. Will put this down to your understandable anger. Ban you? Hell no.
Honestly, I do not like these things happening. It is not what we want, but the reason the for sale forum is so active is because it is open to all.
Can't think of any other forum where there is any buyer protection - for good reason.
As a parallel, STW have no number of posts, no feedback forum, and no visible moderation. Essentially its free for all. We have more than that already while maintaining a workable board.
If I am unsure about a seller I will ask his address and phone number. If genuine, should be no reason why he/she wouldn't give it out. How do they want paying? What is the content of previous posts? Have they been on any rides before? Does he have a feeback thread? All clues.
In this instance, someone may have his address/phone number already. Give him a call - often its all thats needed. Call him again. and again. etc. Won't be long before that £20 whatever is worth it to stop the calls.
If you have his address, write to him. Lots. Go and say hello.
Is he on any other boards with same username? Does anyone have alternative mail addresses?
At the moment, he has not answered mails to several people. May be genuine reason for this, may not.