So I was banned for the dumbest reason ever, Getting scammed to many times in a year, yeah. that's insane.
Anyway I been trolling and bugging eBay support a lot, mostly for fun.
My day job includes lots of calls to tech support so I know my way around tech support. I even tricked one rep in the live chat support to tell me to look up porn. I bet I got him in hot water after asking for his super. I got another rep to look up photos of STD infested privates.
Anyway after a few weeks of bugging eBay I was able to find a few things that can link accounts that may not be very well known.
1: Cars titled in your name.
Yes if you buy a used car that belonged to a banned eBay user you may get linked. This makes a lot of since as eBay used to ask you about what color your car is when lifting your selling limits.
2: The CPU and OS version on your computer.
Working in IT I know its not hard to pull the cpu and OS from a website client, go look up "user agent". Good thing that can be simply changed with a user against switcher.
3: Business/sole partnership or EIN in your name.
So it looks like eBay can look up who owns a Business and link you now. I'm guessing that LLC's are ok but don't take my word for it.
4: Home titled in your name.
So if you buy a new home eBay may be able to link you if you keep other info the same like your name.
5: Installed adorns in your web browser.
Working in IT I know that one can pull a list of addons installed with most web browsers by default and IE can tell the web server a lot of detailed info about your system.
When it comes the 1: 3: and 4: I was able to find out that eBay only uses this info after it can conform that your linked. So simply getting banned from buying a car or new home will likely never happen.
Also note, I was not able to find anything in regards to eBay linking account by MAC address.