Moving to Canada requires moving out of the US. People can, and mostly do, have a presence on more than one social media platform. This is more (exactly) like "I'm not using Digg anymore if they don't role back the changes", which actually happened.
That crowd has been around for every presidential election since I was old enough to understand what it meant. Don't remember one person ever carrying out with the threat from either side.
However, this comment is a decent litmus test on how I can safely ignore anything from them after that point.
I remember the "I'm moving to Canada if Bush gets elected" crowd.
Dukakis lost and as far as I remember nobody moved.