The problem with Lisp is that parenthesis are common in regular grammar. {{ is not.
Of course input from the user should be escaped, but prompts given by the programmer may have parenthesis and there's no way to disambiguate between the prompt and the DSL.
It's not so much against lisp as double curly is a classic string templating style that is common in web programming. I saw it first with `mustache.js` (first release around 2009), but it's probably been used even before that.
Of course input from the user should be escaped, but prompts given by the programmer may have parenthesis and there's no way to disambiguate between the prompt and the DSL.