In the normal textarea, pressing Tab will move the cursor to the edit summary field. Using the WikiEditor editor, it goes to the next focusable element, which in most cases (including the MediaWiki default) is a link to the copyright page.
Tabbing should go from the Wikieditor to the edit summary field.
Tested r61651 on Firefox 3.5.6 on Fedora 11
Version: unspecified
Severity: trivial