Tuvok is such an example as he is almost always referred to as Lieutenant and later he's promoted to Lt. Cdr properly, but he wore Lt. Cdr. rank insignia for like maybe the first season without anyone really correcting it.
It's true that Tilly was not 'promoted' to any rank and kept her rank simply being assigned a position, however, I think it's weird for her to be the XO except that she was part of the principle cast and they needed to give her a reason to be part of the overarching narrative for each season.
I mean let's be clear for most of Ferengi history women were not allowed to own property of any kind - including clothing and some of their business endeavors include poaching endangered animals and literally being slave traders. I mean - I don't think there's any indication that Ferengi society was anything more than hyper-capitalist dystopia as a juxtaposition of the Federation socialist utopia. That Rom and Quark are goofy and lovable I think speaks more to how bad every other Ferengi is operating outside of a Federation station.
From the Federation's perspective the Ferengi are harmless and in this way they may be ethical enough to not warrant confrontation, but at the same time - the Federation does seem to stop them when they're doing something like slave trading so I think we can imagine that for some people in the sphere of Ferengi influence they're not so ethical.