Hi Tom,
I believe the not yet available v 2.0 is supposed to work better with call signs, whether it specifically works with /P I don’t know, we’ll have to wait to see.
I can see that we are all going to be forced to “upgrade” to Ver. 2.0, because seemingly it is not compatible with earlier versions. The following has appeared on the ARRL website:
"“The new protocols cannot be backward compatible with the existing ones,” K1JT said in his post. “We will probably provide some temporary ‘bilingual’ capability for FT8, but not for MSK144. It will be essential for users to upgrade to version 2.0 in order to use the new features and communicate with others who have made the upgrade.”
It might depend on whether both you and the other station has the latest version of the software. I did a test before I emailed you and it gave me the /P in the initial reply.