All,

We saw two presentations by network architects at the RIPE meeting that
used bits in their IPv6 addressing plan to carry meaning beyond simple
network topology and packet routing.

For example, declaring a specific bit in the address to be 1 for voice
traffic or 0 otherwise.

There are motivations for doing this, which may or may not be valid in
any particular case. There are ways to lessen the amount of addresses
consumed by this (for example by assigning /56 instead of /48 to end
users).

But I think that the important thing is that we have historically not
considered this sort of use with address allocation policy. In face,
RFC 2050bis was *just* published as RFC 7050: