I tried setting widows and orphans to 0, but that still produces odd behaviour.
A setting of 3, for both, is working rather well. I have cycled through all the font sizes and there are no spurious breaks. The same page, with the default setting (orphans 2, widows 2), creates these breaks with some font sizes (obviously because that determines how the lines break up). The 0, 0 setting does this too, but not 3, 3. It's some kind of crazy magic, but it works.
