I showed up in Scotland in my OD Utilikilt on our second trip. We stopped in a little tea shop and the two ladies that ran it commented favorably on it and wished that more men would wear a kilt regularly. When out and about in a tartan kilt it was either a none issue or I received good comments. One inebriated gentleman did mention that he was a McDonald while I was wearing Campbell kilt. He followed up with the fact that the troubles between the clans was ancient history and didn't apply to us. I usually wore my hiking boots with the socks scrunched down. I think it'll be fine for your friend to wear a kilt. Generally people got more friendly when they heard my accent. Once they found out I was from Tennessee they got all excited because they all know about Jack Daniels. Surprisingly, many I talked to had visited TN on holiday and enjoyed their time there.

YMOS,
Tony