> One problem is that there are only so many punctuation characters in ASCII
You can use sequences of punctuation characters, e.g. <:= and =:> for brackets, or =>> for an operator, or :*; for a separator. Or use punctuation characters not in ASCII: there's hundreds of them in the symbols blocks of Unicode.
This is certainly true, but I don't think it offers much practically. I would prefer to use a language that re-used or recycled keywords made up of letter than use a soup of punctuation just for the sake of being different.
You can use sequences of punctuation characters, e.g. <:= and =:> for brackets, or =>> for an operator, or :*; for a separator. Or use punctuation characters not in ASCII: there's hundreds of them in the symbols blocks of Unicode.