On macOS 10.13.3 with node 9.4.0, I get these warnings printed after opening and closing node's manpage via man node and q:

`R' is a string (producing the registered sign), not a macro.
`R' is a string (producing the registered sign), not a macro.

Versions of tools involved in man processing:

# groff --version
GNU troff (groff) version 1.19.2
GNU grops (groff) version 1.19.2