Offer / counter-offer? Audiogon rules

I like the system as it is set up with the counter offer in place, with that said I made an offer on a turntable, a brand I wanted to try, that was 10% lower than the asking price which the seller declined and I moved on, about 3 weeks later he reached out and asked if I was still interested and I purchased it for my original offer. The seller was a member in good standing and I left him his positive feedback but he never left mine for me, just chalked it up to maybe he was a little upset at not getting his asking price, but who knows. I also use the counter offer system to great effect when selling here and on the other sites. Enjoy the music

I have found that if I state that "This is my only offer, please no counter offers"  I can let the person know what my thoughts are ??  

The current system works. Unless of course you counter an offer you wish you hadn't.

This thread gets me to thinking...I'm a licensed Realtor. Let's say I list a house for a client for $500,000 and we receive an offer for $450,000. We could counter, for example, at $480,000. Here's the rub: while the buyer is mulling over our counter-offer, we receive an offer for full price. Legally, however, the first buyer has the prerogative to accept our counter despite our having a second buyer willing to pay more. In my practice, I don't counter: I invite the buyer to make a new offer just for that possible scenario. If you counter on Audiogon, does the Buyer have 48 hours to accept or decline? 

the 48 hour rule is the reason I also never do counter offers...