So after this length instead of having the probability to see a character to be virtually 1, you have the opposite effect, because programming languages (a human construct) are very regular in the set of chars they use. So you do not need to a repetition of a character to avoid a statistical effect that does not occur. Being able to choose the escape character, is enough.
The problem is not that it's enough, its that it is too much. Having nine ways to say the same thing is too many; having infinitely many (e.g., nonces) is worse. Having used the "pick your delimiter" approach taken by Perl, I find that you are *still* often bitten by the inability to find a good delimiter for embedding a snippet of a program written in a language similar to the outer language. And it surely makes code less readable, because many more things can be interpreted as quotes.
