Correction: numbers in rtl scripts. Unicode says
that numbers in e.g. Arabic are ltr. This is complete BS, but
it is also a fact on the ground that cannot be fixed. Extra
credit: estimate the cost of this very fundamental mistake.
I'm not sure it's a mistake, it may be a well-though design
compromise.
In arabic, the numbers are written in the same orientation as we do
in european languages, because of a double inversion: from right to
left, they first write the unit, then the 10s, then the 100s... the
end result being that in both writing systems, the units go to the
right and the heavier digits go to the left.