As it is, the CAPTCHA doesn't appear until you try saving your edit. If the CAPTCHA will definitely be displayed for an edit (because $wgCaptchaTriggers['edit'] or $wgCaptchaTriggersOnNamespace[NS_FOO]['edit'] is set), we should show it on the edit page before the user presses "Save page."
Version: unspecified
Severity: enhancement
URL: http://lists.wikimedia.org/pipermail/mediawiki-l/2009-July/031468.html
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=9406
https://bugzilla.wikimedia.org/show_bug.cgi?id=73070