Cmon, now. Apparently using a hyperbolic writing style is grounds for marking things as "unclear".
The question very clearly describes a scenario in which the UTF-8 standard would have to be greatly expanded, and the effects/feasibility of such an act. The question has garnered many direct and concrete answers ranging from historical considerations to mathematical limitations.
One argument for the closing of the discussion was that it would be hard to search for (I'm assuming that's the reason for throwing a random link at me, anyway). However, aside from SEO considerations there are, at the time of this writing, 40 questions tagged unicode and 15 tagged utf-8.
If the answer to whomever's question cannot be found among the 52 questions on this site because of the way the question was posed, then they're not going to find it on this site at all.
It was garnering a good amount of information that I have yet to find aggregated into a single place other than the RFC for unicode (which doesn't address alien invasion hypotheticals, mind you), and the closure of the post yielded a missed opportunity for a potentially revealing and informative answer. Not to mention a diamond mod closed it in a mere 30 seconds or so, which leads me to believe it wasn't read in-full to begin with (link is generously written by one of the opponents to the question at hand).
Is this what I should expect from Programmers.SE?