They aren't sufficient to get rid of the slanderous message on their own - even with an EV. You need to have a bit of volume first. Makes interacting with your first few customers lots of fun.
We actually switched certificates (from StartCom to Globalsign) and the signing was wrong at first, so the message kept showing. When we fixed it, it went away immediately, even though certificate and author name changed...
Here's the article:https://blogs.msdn.microsoft.com/ie/2012/08/14/microsoft-sma...
"Programs signed by an EV code signing certificate can immediately establish reputation with SmartScreen reputation services even if no prior reputation exists for that file or publisher."