Hello Fossilhunter. Sorry I'm a bit late to this thread. If I might ask a couple questions:

How old is the kilt?

Have you used detergent with Fabric Softener in it?

If the answers are "under a year" and "no", then it's a bit of a mystery to me. Though the mill uses a Teflon coating which also has "anti pill fibre technology" properties which decreases the likelihood of pills on the cloth, over time and through dozens of washings, the coating eventually comes off of the cloth and the pills do start to happen as it IS synthetic material. Pilling happens to EVERY type of garment made from Poly, Rayon, Acrylic, etc... some sooner, some later.

I personally have a couple PV kilts that we made 10+ years ago and they do have some pilling, but it didn't show up for several years of somewhat regular wear. The PV we use is the best we can find in the world, but it still is synthetic and will eventually start to pill.

All that being said, the sporran chain might prove a better idea for your kilt than the strap. The strap, being cut square, can rub over time. The sporran chain, having a flat link with welded joins (with no burrs), might be a bit easier on the kilt.

Just my $.02