DyNaMiX: yes, there is at least a few known cases of this. For example, there's Najji Ragitagha whom LOAF already mentioned (although I think this one's a bit iffy... in my opinion, it seems more likely that the people compiling the Victory Streak simply slipped up, because it would be weird for a commoner to use the name of a noble clan as his surname). I believe also at least one of the WC2 Kilrathi aces was mentioned as being a commoner (Kur Human-Killer?). And of course, if Dawx Jhorrad became the captain of a dreadnought in spite of his birth, we can assume that in general, low birth does not stop highly-talented Kilrathi from reaching higher ranks and fame.
McGruff said:
So I take it the nars are the most noble of the honorifics?
According to available information,
nar means simply belonging to a certain clan. So, rather than beiong the most noble of the honorifics, most likely it is the most generic, because (as I understand it) all Kilrathi are associated with a clan in one way or another.
Probably the best way to understand how all this works amongst the Kilrathi is to look at similar societies on Earth. If you look at tribal societies on Earth, they very often have rather complex social systems - a person belongs to a tribe, a clan within that tribe, a specific matrilineal group, a specific patrilineal group, sometimes some additional structures... and then, on top of that, he's also identified by the name of one of his parents (e.g., Osama, son of Laden). So, as you can imagine, there's like a dozen different honorifics that can be used... and that's not even including "special" titles ("defender of", "destroyer of", et cetera).
Of course, just understanding where all this honorific variety
might come from (might - because obviously we can't be sure) doesn't help us all that much, since we still don't know what all these specific honorifics mean.