Use different IDs for buying and for selling.
On your buying ID you can set up private feedback.
Sellers cannot make their feedback private.
If it is your family you don't want snooping, change your ID and your password, and don't tell anyone.
Close your eBay when you leave the site.
The most important thing to remember is that practically no one cares what you are buying or looking at or researching. And your ID masks your actual name.
