Shirt tucked in or out?

[Tobus]

Yes, FossilHunter, it may have to do with the inverted triangle shapes like you described since the kilt is open at the bottom. But it also has to do with proportions of the visual lengths of each segment and where the separation between the two is placed. With a tucked shirt, it seems to let the chest be emphasized, tapering in to the waist where the kilt starts (for those with an ideal body shape), then flaring back out a little as it goes down. The separator is well-placed. But with an untucked loose shirt, it just becomes like a hanging sack overlapping another hanging sack. There's no clean separator between them, and the shirt takes up more than its fair share of the space.

Strangely enough, the last few years I have gravitated towards wearing untucked shirts in the summer when I'm wearing shorts. I consider it a function of decreasing tolerance for the Texas heat, and I'm starting to heed the advice of experts who recommend loose-fitting light clothing to avoid heat stroke. A loose linen button-up shirt, untucked, is a great relief in the heat. But I don't have any problem with the visual aesthetic when paired with shorts. If I did it over a kilt, though, it would just look all kinds of wrong to my eye. I can't really explain why.