Well, yeah, but a post on a self-hosted blog can be posted to HN just as easily as a post on Medium can. And it's not like having "(medium.com)" next to the submission is going to drive upvotes any more than having "(yourdomain.xyz)" would. (For me it actually has the opposite effect; there's so much empty "thought-leader" drivel posted at Medium that seeing that domain next to an HN submission makes me less likely to click through.)

So I guess the question becomes: does Medium function well enough as an aggregator of its own content to make posting there worth the tradeoffs? Does it drive enough traffic from other Medium readers to your own Medium posts to justify giving up everything you have to give up to use the platform? (That's the theory behind Medium, of course, but what I'm wondering is how well it actually works in practice.)