It was announced in this post as road map for Fork 0.15:

Lost Password Recovery
Any account can nominate another account as a lost password recovery agent. This agent will have the power to request a reset the owner key after at least 60 days of account inactivity. If the account is still inactive 30 days after the password reset is requested, then it will take effect.

Users must opt-in to this feature. By default the recovery agent will be @null. A user can opt-out of the feature at any time by changing the agent back to @null.

Seems it was never implemented fully...