I'm still figuring things out on this unique new platform, but here's my list.

1. Dynamic Tags
   Users can add tags to any post, and each new visitor can see and vote for the top 10.
2. Posting Enhancements
   If you want beautiful posts, you need to make it easier for the general populous to enhance their comments & posts, at least build the styling features of Markdown into the editor itself.
3. Follow Feature
   As OP has said, this is a no-brainer, and it seems to be almost already implemented.
4. Native iOS & Android App
   Pay someone, it's a must to expand the "readers" audience.
5. Embeddable quotes
   Similar to other platforms embedding of posts, I think we should have an embeddable "quotes" so, instead of embedding the whole post you can choose which words to quote and other websites can use this content but also send traffic back to the original content.