Feature - Ability to Ack purple?

Does anyone else think it would be useful to have the ability to ack purple?

On the one hand, I understand that purples are outside the existing model
of how acks work. On the other hand, operationally, without ACK there's no
way to indicate that someone has taken ownership of a purple and is working
it, other than signing it out. And we hate signing things out because that
hides information.