Add a trivial hint about using REINPLACE: avoid using comma as the delimiter. (This can mess up e.g. CFLAGS modifications.)
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.