WAAB, the same article notes that the declaration of anathema by a Pope basically counts as an implied piece of infallible teaching, as by doing so it satisfies the conditions of defining a doctrine of faith and/or morals that must be held (contra to the anathema) by the whole church, thus also satisfying the condition that the Pope is speaking in his office as shepherd and teacher of all Christians, and by virtue of his supreme apostolic authority.
We know of notorious cases where a Pope declared something anathema and then had to reverse later, of course (such as declaring acceptance of any Latin translation other than a particular one just made to be anathema–and then discovering that the translation was in significant error somewhere, requiring an updated reprint for the new translation!)
But if that’s true, then papal anathemas don’t necessarily hold; but if papal anathemas don’t necessarily count as infallible teaching, then anything similarly meeting the conditions doesn’t necessarily count either.
Alex, nifty though that is (a Pope on Twitter feed!!–who would have thought I’d live to see the day…), it isn’t any different than the standard Arm doctrine in itself. The “redeem” language sounded more interesting earlier, because the RCC has previously held assurances much like Calvinists about the assurance of salvation for those whom God has redeemed (which is where the Calvs historically traced their emphasis through). But I can’t find anything in the Catechism indicating those whom God redeems He will surely save into the life of Christ.
(I can find that in St. Paul, but not in the Catechism. )