Thanks for writing this up! I've made some minor changes to how Quill displays error messages now, as well as tweaked some copy to make it address users rather than developers. Quill started out as a tool to help debug Micropub implementations, so all the copy was phrased to address the developer of a Micropub endpoint. That was before https://micropub.rocks existed. Quill later evolved to be a much more robust client that can create a bunch of kinds of content, and I hadn't yet gone back through and updated the text. It's clear this has become necessary, so hopefully these changes make a difference now!