does anyone know if you can use the tor browser, to sign into 2 ebay accounts from the same pc
Of course. You can just use an incognito window too, depending what you're trying to accomplish.
Any downside to using TOR (vs. Chrome)?
http://www.aspkin.com/forums/multiple-ebay-paypal-accounts/62089-tor-browser-can-i-stay-stealthy.html