Karl Beckman WA8NVW - NNV5BH
Regarding use of the callsign suffix /R, the FCC in the USA previously required amateur repeater stations to use the /R suffix if they used a Morse code identifier rather than voice. There was also a period back in the 1970's when new repeater station authorizations were issued calls beginning with WR. Both of these USA/FCC policies have since been abandoned, but the use of '/R' in any context is not currently prohibited by the FCC in the USA.
The other common use of "/R" in amateur contesting is for 'roaming' stations in some grid square events. I'm not an avid contester, therefore those details should be explained by those who have the knowledge and experience. In all cases, amateur operators should be aware of limitations on the use of call signs imposed by licensing regulators and the amateur best practices.
If I read the online WSJT help files correctly, the wizards of WSJT indicate that in FT8 Contest Modes, appending the /P suffix will suppress transmission of the 4 character grid locator in the "CQ" message. If a country's regulatory agency requires that location data be sent when an amateur station transmits using FT8 mode at other than the operator's permitted location, the operator can't also append the /P suffix.
Last, thank you, Roger, for serving as a moderator of this group, usually a thankless job at best. Know that your work is noticed and appreciated by many.
Karl WA8NVW OH