I think it's innate that having differentiated syntax for different types of grouping is natural. Look at mathematical papers where people will introduce new brackets with new meanings. (Indeed look at the entirety of QM for a clear, simple case)
Common Lisp has left brackets like {} and [] to the user (aka developer). It supports "reader macros", where the user can extend/supersede the syntax of s-expressions.
So, specialized tools/libraries/applications can introduce these brackets for their own use. Examples are embedded SQL expressions, notations for Frames (special objects, in kind of a mix of OOP and Logics), grammar terms, etc.
Thus it explicitly supports the idea of "people will introduce new brackets with new meanings".