I still have no clear idea on what a canononical link is. I do know that I usually write a blog and then modify it a bit for Medium and use the little box Import Story which works beautifully. I add my five tags and publish. Only then to I place the essay in Twitter (removing that bothersome “I just wrote this…” And then I put it into Facebook. It all works excellently. Ocassionally the Import Story does now work so select and paste my original blog into New Story. What does bother me is that Medium will not accept single spacing of poems and other stuff. I love the fact that you can place a link on the page and when you press enter it appears as a neat little box.
If there is one criticism that I have is that it is (understandably) much to US centered. I write in Spanish also but I believe these get lost even when I tag them as Medium en Español, etc.