Can an accepted offer be a lowball offer too?

Something different but not too far from the subject. I once bought a piece here, paid for it, received it quickly, condition was as stated, everything worked. Then in a few days I got a message asking me to sell it back to him for the same price. I politely refused. Later in about a month I got another message with the same request. Both messages were short and polite, no explanation was given. This time I decided not to reply. No more messages. He did sound to me like he very much regreted selling it but for whatever reason had to. For some time I felt like sh-t a little bit about this story but then got over it. Still, there is a residue.

Yeah, buying used on Audiogon is not for everyone, especially if you are not quite sure about how it would work in your system. In any case, if despite your best educated guess you make a mistake and got the wrong piece, just be prepared to sell it and maybe lose some cash in the process, but maybe not. I bought couple of wrong inexpensive pieces in the past here, put them on sale next day, sold in a few days , didn't lose anything on one piece, lost $100 on another. But I never bought or sold really expensive items.
Besides, people are spoiled by ebay where in many cases there is a possibilty of a return, and paypal is usually on the side of the buyer. But with electronics I often see no return policy there as well.