Uncountably many is the correct answer, and yet it's one of the down-voted posts.

Yes, but that post didn't just contain the words "uncountably many", it also contained babble like "it is absurd to suppose there is a universe in which something, if there be anything, does not exist. " which even if perceived in the context of Tegmark IV which argues for the existence of all mathematical objects, it has nothing to do with the Many-Worlds Interpretation that the original poster was asking about, and which is Tegmark III, not Tegmark IV.

So 95% of that post was utterly irrelevant to the question asked, and yet pretending to be relevant. A horrible signal-to-noise ratio.

And yet you complain that it currently has a -1 downvote? It was probably worthy of atleast a -4 or thereabouts.