If The Road to Reality (from which the term omniverse, or "omnium", originally sprung) is not "mainstream", then pray tell what is.

First, words and phrases become recognized in mainstream physics when they become widely used in publications, not when one well-known physicist uses them. There are 15 results on Google Scholar for a search of 'omniverse' within physics, and of those results, none has been cited more than three times.

Second, even within The Road to Reality - for which I have the first edition as an ebook - the word 'omnium' appears only six times in 1094 pages, where they appear within six consecutive pages (p. 784-9) in a single chapter (ch. 29). The index gives only one page reference (p. 783) for this word.

ETA: You disregarded my claim that "you implicitly imply in your root comment that MWI implies the existence of an omniverse [...] but provide no justification for this." This was a main point.

This is a technical aspect of the discussion, and is not contradictory. The point should be clear if one considers the possibility of flipping 100 heads in a row on a fair two-sided coin. For all intents and purposes, the probability is 0, but that it may happen is not in the least prevented or negated were we to consider an infinite ("long run") flipping of coins. Pretty straightforward and not contradictory.

I was taking what you wrote literally, because you remarked at least twice ([1], [2]) that you dislike the lack of technical sophistication in discussions here, from which I concluded that you must mean what you write when you use technical terms. Under this assumption of literal meaning, I contend that there is a contradiction in the two statements that you wrote.

I have nothing further to add to this line of discussion.

Had I devoted the energy to a full-length discussion of the topic, this probably wouldn't be an issue, but (in general) it should be clear that the number of such worlds (or universes) should be uncountably infinite, not countably infinite. That is, the cardinality would be on the order of Aleph-1, at the very least. And I seriously doubt that had any bearing on prase's original point.

But this is the main point in contention! Recall that your answer to Smk's question ("How many worlds?") is

Uncountably many.

Prase and I pointed out that some of your subsequent reasoning and justification for this answer are unclear or incorrect. An argument for your answer is what I would like to see. You state that this is "clear", but again, one of the main purposes of this comment thread is to establish whether your answer is correct or not!

I guess you could read on the topic, if you're interested. I've already suggested at least two (namely, Hawking and Penrose). Do I really have to do all the work? I need to eat and making a living.

I am reasonably well-read in Hawking's and Penrose's texts in popular science. (I assume you are not referring to their original contributions to physics because other physicists are better known for their contributions to MWI.) I still cannot parse your first phrase ("taking the universe as a QM event"). I think I understand what you mean by your second phrase ("QM applied to the universe"). Is the first phrase supposed to have to same meaning as the second phrase?

There is no "tone" here. That is a mind-projection fallacy. If anyone liberated of mammalian instinct can read what I say without imputing emotional overtones thereto, then it should be obvious that my points consist in reasoned discourse without torrents of bluster at all. It's almost as if you people wish to say, "yeah, we can see you holding that 9mm, just waiting to bust a cap, and the foam dripping from your mouth". It's really rather cute.

Then I must remind you that all commenters on Less Wrong are human, with the exception of Clippy. One of the purposes of this comment thread is to establish which claims are correct. If your arguments are correct, then you have nothing to lose by being more persuasive, and I claim that your tone was overly aggressive and not persuasive for most purposes.