Extension:ConfirmEdit/FancyCaptcha experiments

December 2014
On 2014-12-05, we tried disabling ConfirmEdit altogether on MediaWiki.org: no captcha at all for account registration, edits adding URLs etc.
 * 00:17 disabled by 177494
 * 00:35 re-enabled by 177708

Results:
 * Some users more were registered.
 * There might have been some more userpage spam than usual, sometimes by unregistered accounts.
 * Some were blocked by existing filters, which were generally busier. There was no time to test whether AbuseFilter rules would have been enough to stop it.

Conclusions:
 * We're mostly slowing down generic spambots which don't target MediaWiki (they don't even try to login or use valid wikitext)
 * Special:AbuseFilter/24 tweaked, to disallow and block
 * Some simple linkspam, of a kind which regularly gets through, might have become faster
 * Unclear yet about user registration
 * Effects may be worse on wikis with less sophisticated abuse filters. Disabling captchas on MediaWiki.org can be useful to determine what rules should be moved to global abuse filters.