OK
Asking what tartan and what the significance is, however do not argue with the man wearing said tartan that just shows ignorance.

Asking where the kilted gent got his kilt is always welcomed.

Asking in a condescending tone "Why are you wearing that?" Is not welcomed ever.

All of this depends on who is asking and who they are asking. The other day I was leaving home and a little girl about 5 or 6 said to me
"You look B-eautiful in your skirt!" it was so cute all I could do was smile and say thanks.