Happens to me all the time.  It's not a bug, it's a feature.

Ebay actively encourage listing theft to make it easier for smaller, lazier sellers to leech off sellers that invest either the time or money into systems.

I don't really care about them copying my listings aside from the fact that these listings now masquerade as my listings, potentially siphoning sales away and causing branding issues if those scummy sellers deliver a poor experience and the buyer mistakes it for me.

So yeah Ebay aren't going to change it.