When the dress code says "no jeans," that means "no jeans." It's not up to individuals to reinterpret a clear policy just because they encounter a situation that they don't understand. That doesn't mean that there is no work involved in helping others understand why your choices should be considered professional and in adherence with the policy if an objection is raised.

The dress code at my last company had specific instructions for men and women. Even so, it was the prevailing culture that applied more than the policy. I was reprimanded once for wearing an earring (I forgot to take it out from the weekend), but there was nothing in the policy prohibiting that. Meanwhile, the code was very clear that women should not wear sandals or open-toed shoes without also wearing hose, but that policy was violated with wanton abandon throughout the office (even by the HR staff, who, when made aware of this apparent violation, considered rewriting the policy to suit their own preferences).

If there's one thing I've learned after being employed for the last twenty-some-odd years, it's that managers just hate dealing with inter-personnel squabbles. Frankly I think the failure lay with the first supervisor (of the affronted person), who really ought to have advised the person to speak with you about their concerns. So, how did you leave it with the supervisor? Were you banned from wearing the kilt, or just informed that someone had a problem with it? With a cool head, I'd offer to work with anyone who has a concern and the agency's administrators to help bring clarity to this somewhat new situation.

Let us know how it goes.
Rex.