The wearing of medals, usually miniatures, on civilian suits used to be fairly common, especially in the UK and on the Continent. Not so much in the US but you did see it occasionally at veterans events.
In this archaic formal setting, I am sure it is perfectly appropriate.
Thanks. I looked back and it happened at Philips funeral. Princes were not in uniform by orders of the queen. princes wore medals on their civvies.
You are right about the veterans,
The Marine Corps league allows the wearing of medals ...either service or league medals, but one must be in “official” league uniform.
as an aside...it took forever but it became specified as such (I think)in 2008 that veterans could salute the flag:
members of the Armed Forces and veterans who are present but not in uniform may render the military salute in the manner provided for individuals in uniform;