Because of his original purpose, it makes sense that the Doctor wouldn’t have held a Starfleet rank during Voyager.
However, in Prodigy, he still doesn’t have pips. This leads to my questions:
- Can a self-aware hologram hold rank or a non-com position in Starfleet?
- If so, how would the Doctor attaib it?
According to the STO wiki, he doesn’t wear them by choice but does have a rank. That might be a reasonable explanation; I can’t imagine Janeway not at least trying to field commission him.
Even without an official rank, on Voyager he was still considered a Department Head and (more importantly) the CMO, which gave significant authority (even exceeding the Captain on certain medical matters), regardless of whether or not he was ever given any pips. The same thing would likely apply on subsequent postings.
If he ever had to be assigned a rank for clerical/administrative purposes, it would probably be the default required rank for a Starfleet CMO candidate for the class of ship he was serving on.