When you try to create a new page via action=formcreate it results in a weird Javascript redirect which drops the tokens, resulting in an `It appears that your browser does not support Unicode. It is required to edit pages, so your edit was not saved.` error. Clicking save again will be successful, but the whole experience is somewhat confusing.
It seems that when formcreate is submitted, it generates a blank page with an invisible form and an auto-submit-on-load JS script on it, as a way of generating a POST redirect. The form (which points to the normal page edit form, action=submit) does not include the CSRF token, nor the unicode check, so the form submission fails.
Surely there are better ways than this to redirect a form to another one. But the very least, the redirect form should include the CSRF and Unicode tokens.