I would think that with the CC backup you have two layers of protection as well.
Using a debit on line does not, I believe, provide the same protection as a credit card. At least you're insulated by Pay Pal in this case.
I have had one bad Ebay transaction and Ebay Buyer Protection stepped in and forced a refund.
I lost shipping costs. Plan on that if you have a bad one.

A fool was selling customer-returned (used) reels and calling them new.
Always hide your email address and keep all correspondence within the Ebay message system.