A few weeks ago, we hosted a discussion thread in which we asked writers what features they’d like to see in Substack. We got hundreds of responses, asking for everything from image captions to a mobile app. We were energized by the discussion, and just a little intimidated. To build something great, we have to stay focused and say no to a lot – there’s no way around that. But on top of that, we’re a team of just three people –