I have bought and sold a lot on Reverb and never had a bad experience with Reverb. It is the problematic sellers and buyers that are the real problem. I have been fully covered in the few cases that have arisen except for one case which was really not completely Reverb's fault.
The one case where I did lose in the process involved a buyer claiming a Neumann M147 tube mic was defective. When it was returned, it was obvious the supplied cable was replaced with a damaged one which I could prove through pictures (I think this was the plan of the buyer in the first place and they filed a claim a few hours after the mic was received). Reverb covered the $299 cost of the cable, however, the bad cable ended up damaging the mic and power supply. I could not prove it, but I know everything was working when shipped and it did not arrive electronically fried. I ended up eating the over $500 repair bill and it was confirmed the cable shorted the power supply and mic. This was several months after the transaction and the case was already closed. There was nothing I could do at this point and it was not Reverb's fault due to the elapsed time. For this reason, I am very thorough and forthcoming with sales descriptions especially about condition and use a lot of pictures. This has saved my ass a few times and Reverb resolved the bogus claims in my favor both as a seller and a buyer.