Auto focussing the editor may help make clear that the text is editable. This is currently done in the single instance TinyMCE prototype.
It may be too early to optimize this far, when it's still mostly the prototype that's being tested. I wouldn't think it unlikely that some of these aspects change once the surrounding admin chrome arrives. At that point you will have intentionally navigated to a "Write New" page, and you'll see publish buttons around the editor. Perhaps this puts people in a better mindspace.
Let's definitely keep the ticket open as something to explore later on, if it remains an issue.
Going through some of these open questions, let's close for now until we start refining a single prototype / direction.
Most helpful comment
It may be too early to optimize this far, when it's still mostly the prototype that's being tested. I wouldn't think it unlikely that some of these aspects change once the surrounding admin chrome arrives. At that point you will have intentionally navigated to a "Write New" page, and you'll see publish buttons around the editor. Perhaps this puts people in a better mindspace.
Let's definitely keep the ticket open as something to explore later on, if it remains an issue.