REINPLACE does not exist.

This comes out of nowhere, one wonders what uses cases it is trying to fix.

Hints usually comes by the form of a <tip> tag, and it usually goes along where something is defined. In this case, it should go in https://www.freebsd.org/doc/en/books/porters-handbook/slow-patch.html in 4.4.3. Simple Automatic Replacements.

Comma , is often chosen as the delimiter because of its very little occupied space which helps readability. Pipe | is okayish, I use it sometimes as well, colon : and semicolon ; also look fine. At-sign @ and hash # are quite heavy and interlink with the actual editable text, so I'd avoid them.

That said, there's no "always good" choice. We avoid slashes / because of the path separators, and similarly we can simply avoid commas , when dealing with compiler/linker options, but PHB should not recommend to never use them.