I don't know since when, but if an anonymous user edits/creates a page in Page: namespace then the page quality level is changed to "0" (= no text).
(This doesn't seem to be the case in the German Wikisource, where anonymous users have radio buttons to change page status.)
Default behaviour used to be that if an anonymous user edits a page then the quality level is set to "1" (new page) or there's no change in it.
Version: unspecified
Severity: normal