I see your link and raise you Prepitch: Character integer literals - #25 by allevato. regardless which route you go down the point is the same you can only claim a character once and I’d be disappointed to see a whole character ‘ squandered on something as niche as raw strings.
There are many other problems with using ' and ` that have just not been thought through. Using repetitions of the quote character will confuse external editors, mean you can no longer detect multiline raw strings and create problems using the quote at the start of the intended string that are not solved by adding more rules such as requiring an odd number - what if you want two quote characters at the start of the string. The more general statement is that you really need to have a different character for the extra delimiter than your quote character at the least such as ##”a string”## or \\”a string”\\ which isn’t all bad. I'd keep “” for strings with some other indicator or prefix to engage special treatment of it’s contents rather than add something so syntactically distinct to the language as ‘.