Visible souls....

[littlemanpoet]

But that brings us to a problem with your definition of a "visible soul" character. ... These sound more like techniques of portrayal than characteristics of the characters themselves. - Aiwendil

Well, you did ask for what in practice, in literary terms, it means for a character's soul to be visible. "In practice" has to do with technique. Did you intend literary meaning instead? That's a different kettle of fish. Of my three points, the first is least technique oriented: a minimum of internal psychological processing by the character(s), whether in terms of thoughts, feelings, or dreams. For the second, let's say that character(s) are real, three-dimensional beings, and hold the technique with which that is evoked as distinguished from the subcreation of them. As for the third, we could say that internal attributes are not hidden from those who have eyes to see, according to the laws that govern the mythic setting.

This is speculative, but I thought I'd give it a go.