The idea of suggesting relevant territories to post in is really nice, it could be easily determined by the contents of the post title itself.

Another option for the territory selector is to have it blank each time a user click the post button. So user are forced to select a territory, not just post in the latest territory they were reading from.

The "new post" flow is currently complex and look's is satisfying the system architecture more than the user needs... info hierarchy is also accommodating technicalities. If I could recommend something, this would be for me an ideal form to post, where the input fields are displayed once the user chose the type of post to be published, then the territory.

So when a user hit /post s/he always gets redirected to https://stacker.news/post no matter which territory is coming from.

Last suggestion; the post button should always be visible and available, also when reading a post... quick fix? add it to the footer!