I guess I have a high risk tolerance, but I don't have any issues with eBay. I have three bags I've bought on eBay (two Kellys and an HAC).
I buy from sellers with a long track record and perfect/near perfect seller feedback. Professional eBay sellers don't want to hurt their own reputations and will generally help solve any problems.
I usually authenticate with Bababebi prior to purchase (no, eBay does not use outside authenticators, they use their own team, one of whom apparently worked at Hermès - not that that is necessarily helpful). I always get a bababebi cert at some point, for any bag where I don't have a boutique receipt. I am also comfortable with my personal knowledge and ability to authenticate. (FWIW all my eBay-bought bags have been to spa.)
I always pay with PayPal using a credit card with purchase protection. Both eBay and PayPal will side with a buyer 99.9% of the time (just ask anyone here who sells on eBay). Amex and Chase Sapphire will cover purchases up to 10K with no questions asked.
I have purchased one H bag on eBay which was returnable; I did want to return it (this was a pure change of heart); it was a painless and easy process. I actually bought another bag from that same seller.
(I have also sold bags on eBay; the only reason I don't do this anymore is that it is too time-consuming and harder to do in the EU.)
I think it's very much up to one's comfort level with Hermès authentication; with knowing colors, leathers, and years; knowing the market and whether something is too good to be true; with assessing sellers; and with understanding payment recourse.
FWIW I have never seen a big reseller get H colors and leathers right 100% of the time; this includes Sothebys and Christies, where they literally have a team of "experts". So I don't necessarily get all bent out of shape if a description is off.
What I will not do is buy anything that's final sale (looking at you
TRR) and I will never purchase from anyone who asks for bank transfer or any other irreversible payment method.