C.E. Evans wrote:
Personally, I like to think a fleet captain is a grade between captain and commodore with the rank insignia being three full stripes.
It could be. But it could also be a rank above Commodore since we've only seen "Fleet Captain" mentioned once in the entirety of Trek.
It could also be that "Fleet Captain" may be a special rank created solely for Christopher Pike as recognition for something unique he did in service of the Federation/Starfleet.
We just know so little about the rank, we can let our imaginations run wild.