I've been using Paper since October, and thus far it's been my favorite Markdown Editor. It's not perfect, but it does a great job of accepting inline markdown

I've been using Paper since October, and thus far it's been my favorite Markdown Editor. It's not perfect, but it does a great job of accepting inline markdown and then just getting out of the way. Also, you can export from Paper to Markdown or docx. I've written a few of my github READMEs in Paper and then exported to Markdown and they've worked just fine. The examples you've mentioned (ctrl-i, ctrl-b, insert hyperlink) all work just fine, as does pasting markdown directly into the editor. -- I have nothing to do with Dropbox, except as a happy paying customer and a happy Paper user.