C.E. Evans wrote:
Actually, it is. It doesn't have to be literally termed as commissioned and noncommissioned, but there is indeed a distinction between those who do "grunt work" and those with administrative duties. And as with police departments, it could be easily be a case that all Starfleet personnel could be referred to commonly as officers regardless of their actual rank or duties.
No, it is clear that not everyone in Starfleet is considered an "officer" the way members of a police department are. In "The Drumhead" Picard asks Crewman Tarses whether he ever considered going the Academy "to become an officer." That line would make no sense if all Starfleet personnel were "officers," since Tarses is clearly serving in Starfleet at the time.
No it's not. Benjamin Maxwell called O'brien his best tactical officer he ever had in the Wounded. In Rules of Engagement Worf described him as an outstanding officer. I guess since he's technically an NCO that could fly, being the last O does mean officer, but it gets even more strange when he routinely has officers(ensigns and lieutenants) working for him on DS9.
O'brien does go out of his way several times to describe himself as an enlisted man, but calling him a Starfleet officer seems to be a catch all for everyone in Starfleet regardless if they hold officer rank or enlisted.