You basically shouldn't do it. BIRD does something like last-resort pointer
comparison and we should probably even add a warning if somebody misconfigures
in this way.

Why not use the protocol's default preference as a last-resort tie-breaker?
It's probably less code than the warning you suggest, and should do something
reasonable in most cases.

Yes, it's probably a more reasonable tie-break. Low priority in the team for now anyway, we're quite busy. patches welcome for both the documentation updates and this last-resort tie-break.

-- 
Maria Matejka | BIRD Team Leader | CZ.NIC, z.s.p.o.