Treewyrm's opinion matches what I was about to say when I first read Jinx's post. A slight deviation from what he have already said, and I agree with him in what he did say, is that there are different qualities of characters.
The more extraordinary the character you are portraying is, be it in terms of the power he is available to tap in game (PvP aspect), be it in its uniqueness, the more difficult it is for you to role play it and for others to role play to it in turn (ambiance aspect). It goes somewhat in the same terms of the already stated "big ship leads to big responsibility", but I'd rephrase that to "big role leads to greater concern in conforming to a sensible ambiance".
This veers away from the size and power of a ship, but includes it. I wouldn't say that it's acceptable for a Rhino pilot to be out of character, but I'd say it's more acceptable that a player portraying a Rhino pilot be more lax about that role. He may very well portray an irresponsible or not sane person without imposing (both on the PvP and ambiance aspects of role play) himself too much onto others. An unique character such as the captain of a gigantic and powerful ship or a very out of the ordinary character/ship does impose onto others and there's where lies the issue.
It's not "okay" for anyone to be out of character. But its "okay" for a small role to be portrayed in less depth than a very big one. Or, in other words, the bigger the role, the bigger the responsibility or even, the bigger should be the concern in conforming to a sensible ambiance.
EDIT: That being said, it would be much nicer if you thought about the implications of flying extraordinary characters prior to doing so.
Like in:
"Hello. I'm a ghost. I'm going to kill you."
"Wait, what?!" (Pew pew pew, BOOM!)
"//jerk"
...as opposed to:
*static*
"What the hell?"
*screams of the damned*
"Errr... Are you okay?"
*You feel an eerie sensation running up your spine. The fighter ahead of you have a blueish fiery aura around it like something you've never seen before.*
"What the hell is this?"
**Do you fear death, living?**
"I'm out of here."
**Death will take its toll now, living. Prepare to meet eternal doom.** (PvP aspect of role play starts)