That's how quoting works by default in m4 and TeX, both defined in the 70s. Unfortunately Unicode retconned the ASCII apostrophe character ' to be a vertical line, maybe out of a misguided deference to Microsoft Windows, and now we all have to suffer the consequences. (Unless we're using Computer Modern fonts or other fonts that predate this error, such as VGA font ROM dumps.)
In the 70s and 80s, and into the current millennium on Unix, `x' did look like ‘x’, but now instead it looks like dogshit. Even if you are willing to require a custom font for readability, though, that doesn't solve the problem; you need some way to include an apostrophe in your quoted string!
As for end delimiters, C itself supports multicharacter literals, which are potentially useful for things like Macintosh type and creator codes, or FTP commands. Unfortunately, following the Unicode botch theme, the standard failed to define an endianness or minimum width for them, so they're not very useful today. You can use them as enum values if you want to make your memory dumps easier to read in the debugger, and that's about it. I think Microsoft's compiler botched them so badly that even that's not an option if you need your code to run on it.