I think we all, including Dave, acknowledge and accept that sexing mistakes can and will happen and don't generally attribute anything malicious to it... I haven't read anything in Dave's statements suggesting that he thought the animal was intentionally misrepresented... Just misrepresented.
The debate about selling it as a female is moot... if Neil put 0.1 in the ad, it was sold as a female... if it is not a female (As evidence is strongly suggesting), then the animal was unintentionally misrepresented. If he was uncertain of the gender, there should have been some mention of this in either the ads or the correspondance leading up to the transaction, it's not really honest to state something that's uncertain and rely on the buyer to question it before admitting to the uncertainty.
I think we're all aware enough of hemipenal structure to admit that it's a lot easier to accidently probe or pop an animal as a shallower female than it is to accidently probe or pop as a male. Sure a probe can be shoved too deep, but there is usually a great deal of evidence that this has happened (Vis an unpleasant discharge of blood, blood on the tip of the probe, and... the one time I did accidently do so when learning how to probe myself, there was an unpleasant sensation that something had just given way that shouldn't have and I knew instantly what I had done).
I'll say right now that I know both these men fairly well, albeit I have never met Neil, after reading enough posts and communicating via e-mail I have a strong feeling about his credibility and I am of seriously mixed minds about what should come about as a conclusion to leave everyone happy.
On the one hand, Neil has a twenty four hour guarantee, which would legally protect him from having to refund anything whatsoever and certainly puts him in the technical right even if he didn't wish to offer any soultion whatsoever, with that in mind, his suggestions are more than fair.
On the other, there exist very valid and acceptable reasons for the snake not being probed upon receipt and the communication was immediate after discovering the mistake... it's not as if this occurred months or years after the guarantee period.
Neil has stated many times that customer service is everything, a concept I agree with wholeheartedly... And I'm not certain that he has really lived up to his statements in this instance but I can't pinpoint an area where I can fault him for this in, because he offered something outside of his agreed to guarantee period... I'm also admittedly biased because I vouched for Neil to Dave prior to the purchase, so I'm not being entirely objective here.
I will say that I can see Dave's frustration and understand his comments about not wanting anything back... after a certain point, a defeatist attitude will creep up on all of us and we might make statements of that nature, however I think the only way for both parties to be satisfied here is with some resolution involving the money and the animal... I can also see why he posted when he did, the offer of the return of $50 (which sounds very fair if he had wanted to keep it as a male) sounded fairly concrete, as if it was the only option avaliable, so my opinion is that it was not premature or particularly damning, the wording was not harsh, he was merely informing people of a situation that had occured...
There are now two sources stating the animal is a male, and an unspecified three or four claiming it's a female, although some of those were the result of popping, which I have never found to be as accurate as a personal matter, although it is a difference of degree... The most reasonable conclusion I have seen offered was an acceptance of the proposed complete refund with the additional stipulation that the individual who had been correct about the gender of the animal in question pay for the shipping costs incurred for ALL shipments, both ways... As Neil himself has stated in the past (although I'm too lazy to get an exact quote), if the good delivered where not those paid for, then there exists no reason why shipping should be the responsibility of the buyer. And of course should Neil's determination of gender be proved true, there exists no reason why he should eat any of the shipping costs incurred.
One additional suggestion I have that the repesctive parties might consider... Is there anyone within a reasonable distance of Dave who you would consider trustworthy to probe this animal on both sides Neil? Central California's a big place, lots of people, lots of herpers, surely you know someone you trust... I only add this because, putting myself in his shoes, I wouldn't feel safe returning the animal only to have a vet in Florida determine it's a female again, only to open up everything once more but have the other person holding both the animal and the money... I personally would trust you, but you have not given Dave the same confidence.
Just as a conclusion and an addendum... I seriously hope I have not offended either party involved in this matter as I have a great deal of respect for the people on both sides of this issue and I would not wish to damage my position (such as it may be) with either of you. I feel that someplace here, mistakes were made and I am sorry it had to happen between two individuals who I know and respect... Had it been handled differently by either or both parties, I suspect that there would have been a long and healthy history of purchases established.