I've never traveled with a kilt pin, but I have been traveling quite a bit, and it seems like every airport interprets the rules differently. The small regional airports are easily the strictest; I suspect it's because the TSA agents have the time to go over everyone with a fine-toothed comb.

I actually had a P-38 can opener confiscated as a "blade" at Yuma's airport; I bet they would have taken a kilt pin too. They also took some waterproof matches (they claimed were "strike anywhere" - they weren't) and ran just about every item I put on the belt thru twice.

My guess is that in a major airport you'd probably be OK, but the smaller the airport the bigger the risk.