What a horrible article. They are not "abusing" anything; it's their site and it's common for large sites to deploy nofollow. It discourages spammers from creating lots of outbound links for seo purposes and weakens the overall value of outbound links from their site.
"Medium hosts 300,000 articles published by half a million users, and yet none of these links back to external website, because of something called "rel=nofollow". - what are you talking about? That's not how it works at all. The hyperlinks still operate just fine.
Yes, I understand what nofollow is for. The links do work, but they are not followed by search engines, which means content is not credited, as it should be.
Why should it be? They own the site, so they don't need to give up their link juice to every legit person and every spammer who wants to link out from their site.
Your own link just stated that they enacted nofollow due to abuse and because Google was punishing them by removing pages all together. Then you go on and call them "abusers" for protecting their content. wat.
I'm not saying that removing nofollow for medium is the right solution. That would be inviting a horde of spammers on to the site.
However, there can be better solutions (such as the ones by StackOverflow). Content quality (which can be measured by medium) to allow good quality content have outbound links would be another.
A simple start would be to have a whitelist of domains that can be considered authoritative (as suggested in the linked tweet).
Yes, this is a hard problem, but it needs to be solved.
If they removed nofollow it would influence companies with huge SEO budgets to start working on there at putting out discreet promotional content. You would see services offering links on Medium etc..
"Medium hosts 300,000 articles published by half a million users, and yet none of these links back to external website, because of something called "rel=nofollow". - what are you talking about? That's not how it works at all. The hyperlinks still operate just fine.