In The Elements of Typographical Style, the author notes (§2.4.8) that widows—single lines occurring at the top of a page—should be avoided. Yet the text height of two facing pages should be the same, and so a line should be removed from both pages in the spread (§2.4.9).
I assume that TeX has the ability to perform this kind of check. What solutions are possible (or already exist) to solve this general problem?
The same solution could be applied to orphans, though Robert Bringhurst does not seem to be so concerned about these.