In reply to the Black Tie Guide referenced in a previous post. I would hardly count this as a reference source for wearing the kilt when they say in their opening paragraph -

"Scottish evening dress traces its roots back to the seventeenth century and is as diverse as Anglo-American black tie, if not more so. Consequently, this page is only intended to serve as an introduction to the topic. It does so by repeating the descriptions in the Wikipedia "Highland Dress" article (which has improved considerably since the previous edition of the Guide) "

The section on highland dress in the Wikipedia article was actually edited into the Wikipedia article long after it was written by an X Marker who I don't think is even active here any more.