Followers are mostly benign; they can't do anything except watch to see when you have new listings and if they like it, buy. At one point they liked the items you were selling and click the saved seller button to be notified when you posted new items. If they were up to no good, there are other ways to cause problems with your account by searching out what you are selling by your username.
All someone has to do is click the Saved Sellers button and they become followers. I have several sellers that I have saved that way, having bought from them in the past. I can go to My eBay and open saved sellers and check to see what they have that is new. There is the option when saving sellers to get email or not to be notified when the list new items.
Nice to know that you have followers, but just ignore it.
