In reply to N7UN:
by the HA law if I want to use my radio outside of my registered QTH I have to use “/P”.
Btw we can hear the “/AM” relatively often, too because HA5AQ is a very practiced hang-glider 
73
Zsolt
Signing /MM means maritime mobile, mobile on sea waters.
When operate from a vessel from inland waters is better to use /M.
In ex Yugoslavia there was a rule when the personal station was used by a family member to use callsign/X in case of male member, and callsign/Y for female member, hi.
The stations from Ukraine often use callsign/A when not in the primary location.
The only active station from Mont Athos used callsign/A to make distinction from SV2 call area.
In various contests we can hear callsign/89 to determenie the department area,callsign/NAVAL to determine the club membership, e.t.c.
Adding someting after the callsign is more tolerable when operating on Phone.
We must to obey the rule to give our callsign in clear format and to be carefull when like to add some information which is not related to operating from another DXCC entity, different call area, portable, mobile e.t.c.
The solution for the formal issue related to this is not to use "/“ after the callsign.