It has, it's been live since mid this week. See https://blog.wikimedia.org/blog/2010/09/22/article-feedback-pilot-goes-live/ and it's inclusion category http://en.wikipedia.org/wiki/Category:Article_Feedback_Pilot

The API isn't really designed for end user interaction...

Also

		foreach( $wgArticleAssessmentRatings as $rating ) {
			$ret["r{$rating}"] = array(
				ApiBase::PARAM_TYPE => 'integer',
				ApiBase::PARAM_DFLT => 0,
				ApiBase::PARAM_MIN => 0,
				ApiBase::PARAM_MAX => 5,
			);
		}

The module is offloading the parameter validation to the core API, so it would seem it's a core API bug.. At a guess, it's due to there being no MAX2

CC'ing Roan.

Scrap the MAX2 coment, that's only the case for 'limit' type.

r73742

As per the CR, "Maybe we should have a PARAM_MAX_ENFORCE. Rather than just warning!"

r73743 actually, goddamit!