This (/w/extensions/ConfirmEdit/MathCaptcha/MathCaptcha.class.php) seems to be the place where the Math formula is being converted to a png image in ConfirmEdit/Math extension .

	/** Fetch the math */
	function fetchMath( $sum ) {
		if ( class_exists( 'MathRenderer' ) ) {
			$math = MathRenderer::getRenderer( $sum, array(), MW_MATH_PNG );
		} else {
			throw new Exception( 'MathCaptcha requires the Math extension for MediaWiki versions 1.18 and above.' );
		}
		$html = $math->render();
		return preg_replace( '/alt=".*?"/', '', $html );
	}

instead of asking the Math extension to take care of it. Hence one needs latex and texvc running on one's system to use ConfirmEdit/Math. Just having Mathoid running isn't working. LateXML was not tested.

My System
Mediawiki 1.26.3 with Confirmedit extension, latest Math extension, Mathoid 0.6.3

Thanks