Can an accepted offer be a lowball offer too?

There were two issues but they are related. Once I notified the seller that all was not well, in that he over graded the product, that was when the lowball comment came out, Seller stood by his erroneous grading and would do nothing at all, apparently since he felt that he was lowballed. Frankly, I was taken aback. It's not like I offered 50% of the asking price. It was somewhere about 85% and if I've made an offer, I am serious and I am always prepared to negotiate. Indeed, I now recall another instance when I made an offer on a DAC. I truly thought the seller was on the high side. I made an offer and did the proposed seller tear me a new one for the outrageously insulting offer. Didn't bother with a counter offer, and I found a local guy with the same DAC- we made a deal and I picked it up. With the first guy, we are not talking about your wife or sister so cut the insult stuff. I just don't get why it's so hard for some sellers to politely decline an offer. 

When I sell I'm scrupulous about grading and tend to undergrade. In this internet trading thing, we have buy one thing going for us- a good established reputation. 

And now that I think of it, neither here on audiogon nor on eBay, have I ever once been asked to take something back for any reason, let alone, for being erroneously described, or have ever had a complaint about something not being quite as described. I'm pretty paranoid about accurately describing something. And I truly believe in karma. And I've been trading on line 18 years or so. 

Recently, about two months ago, I was asked to take something back, and I refused. The buyer told me that an amp I shipped him arrived in excellent condition, as advertised. Then, a few days later, he told me that it did not work as well with his speakers as he hoped it would, and asked me if he could return it to me for a refund. I told him that I was not an audio store, and that I do not accept returns due to system synergy issues.
Sheesh, some buyers these days expect it all. They want used prices, but new price services.

Part of this internet trading thing also depends on quality buyers.  Yes, there are some rude and shady sellers. However, there are also some rude and shady buyers. The water is full of sharks, sellers and buyers beware.

I've never been asked to take something back but I have preemptively offered at the inkling someone might be dissatisfied was what I was trying to say. Both times i offered the buyer elected to keep the item in question.

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.