This check box controls whether nested comments (which are comments inside other comments) are supported. For example
(* outer (* inner comment *) comment *)When nested comments are not supported the example comment above will terminate at the first *) so only
(* outer (* inner comment *)will be treated as a comment. When nested comments are supported the compiler recognizes the end of comments only when the number of close comment markers matches the number of open comment markers. So the example comment above will terminate only after the second *).
Both open comment markers (* and { are considered to be equivalent, and both close comment markers *) and } are considered to be equivalent. So attempting to trick the compiler into accepting nested comments with something like
(* outer { inner comment } comment *)will not work.
Nested comments are disabled by default since in Standard Pascal comments do not nest.