If someone has good feedback and the initial communication feels legit (e.g. they can answer questions on the product and seem to understand audio gear and the general jargon), what are the other forms of "due diligence"? I've used phone calls a few times to get a better feeling about the risk involved, but that is no guarantee either.
The sad part is more and more sellers are refusing to accept PayPal G&S which makes purchasing big ticket items a lot more riskier. I get it, I don't like the 1099-K forms either or the possibility a buyer makes a bogus claim to void the deal after the fact, but it definitely limits what sale ads I'll consider making a purchase on. Personally, I've started to accept the fact that paying a bit more for a used item from a dealer or valid re-seller is maybe worth it in certain cases...