Not sure how you got to this, but page names that start with a ! used to be federated URLs, which is a feature that no longer exist. If you still see it, perhaps somehow you have a file on disk with this name?
As to read-only pages, you can now build these using the editor:pageCreating event that I mentioned in the page templates thread. They’re not real pages, but rather virtual ones.
Ah neat, I’ll give that a try. My use case is the same as in the link - my “main” page, which I sometimes access from my phone, and isn’t really meant for editing, and an accidental tap will switch to the source of the widget I want. So you’re saying I shouldn’t look to create read-only pages, but rather replace them with ones rendered on-the-fly by the event handler?