Fixed graph here, containing the top 20 posters by number of posts, for 1000/1315 links containing the medium.com domain. (Using R; sorry about the labels)
http://i.imgur.com/WIJ4cT9.png
...wow, 1,000 submissions for a less-than 1 year startup is crazy.
NB: If you want to get more than 100, you need to use the start=0,100,200... parameter which works up to a maximum of 900 with limit=100.
(http://imgur.com/pDIyeRM)
EDIT: I should have said, this is only the last 100 posts!
EDIT: increasing the number gives a bad request error. :-/