A good way to handle this would be that if both sides agree that they should be shooting each other IRP, its ok to let them shoot each other. If only one side thinks so and the other doesn't, it's not ok.
If one sided shooting of the same ID is permitted, it will probably mostly happen in ways that used to be a common sight when we still had players:
One side decided that they get to tell the other side what to do (ranging from "don't attack your IRP enemy who is my OORP friend" to "don't go to X or do Y because I R boss of it" to "dont fly caps, caps are only for me and my friends") because they are "stronger" (I'm a pro with friends in the right places and ur a noob). It's pretty much translates into "submit to me or shut up or leave", which is the attitude that is and was the root of most of disco's problems.
Agree with Lucas position. There alot of factions for which shooting each others have sense, for example, why in the world one pirate cant shoot/rob another? "Thief honor"? Any loosely organised/not united faction shouldnt have those restrictions. In same moment, for heavily organised factions with clear hierarchy shooting in your own ID pretty clear means becoming rogue or dead.
As well as we need stop this crap with loosely written rules, "blah blah common sense" and precedent law, when precedent was years ago and nobody but 2-3 bitter vets, who dont play anyway, remember it.
I definitely spent time shooting 'allies' that were parked in my preferred pirating lanes back in 4.85 and 4.86 as a Lane Hacker. I don't know if this was disallowed back then, but it never came back to bite me besides having fun little fights with the pirates when they decided it was THEIR TURN ON THE XBOX MOM SAID I COULD PLAY NOW
