Special:MovePage now has a namespace dropdown menu, but on certain wikis (such as the English Wikipedia), I've observed this pattern of behavior:

1. User creates an article draft at "User:John Smith/Turtles and fish".
2. User goes to move the page at Special:MovePage.
3. User removes "John Smith" from the input field, fills in a reason, and then clicks move page.
4. Page ends up in the wrong location ("User:Turtles and fish").

Alternate scenario:

3. User removes "John Smith" from the input field, selects "Wikipedia" (because they want to publish their article on Wikipedia, after all, not realizing this is the site's meta-namespace), fills in a reason, and then clicks move page.
4. Page ends up in the wrong location ("Wikipedia:Turtles and fish").

I'm not sure how to best solve this. My inclination would be to add a confirmation screen (or use JavaScript) to say "THIS IS WHAT YOUR NEW PAGE TITLE WILL LOOK LIKE: 'User:Turtles and fish'. OKAY?" I'm not sure this would help if it read "THIS IS WHAT YOUR NEW PAGE TITLE WILL LOOK LIKE: 'Wikipedia:Turtles and fish'."

This needs further thought.

See Also:

• T31454: Enforce byteLimit for page title input on Special:MovePage
• T36848: Improve mediawiki.special.movePage.js to remove the namespace name when the user paste the full target name in the field
• T62399: When moving, warn if people try to move to Foo:Foo:Bar (repeated namespace)