Agreed, RST headers are too "flexible". They're also IMO quite annoying to write and maintain (exactly matching the title length) or ugly (overlength).
Plus, solving inconsistencies with simple head math: $ to the end of lines to get the character counts from the two line and say, add 3 with 3i=[Esc] or subtract 5 with 5x. With over and under decoration you can . the other side to fixup both.
