The way the links open is strictly up to the link author. AFAIK, no browser can override that behavior.
At some point, the "rel" tag may also affect links as browsers adopt the recommended behavior. rel=external is supposed to open in a new tab or window.
I echo the frustration of everyone writing here.
This is one of the most annoying and pointless design choices ever: you choose to add this feature, you place it directly under the close tab which everyone uses, and you give no option to recover.
A recipe for disaster. If you do not understand it yourselves, having everyone here point it out should do. 1.3K views!
And i'm sorry, but it should be your responsibility to take this input to the proper section of whatever forum. This is customer service 101.
People here have already spent their time to point out the obvious to you, and are already frustrated enough.