jcoffey-dev is traveling from Thursday 1 October through Sunday 4 October. Issues and pull requests are welcome, and will get an answer after that. Thanks for your patience.
Destroying a held account removes the login, as offboarding needs, but
keeps its data as a deleted account with no expiry, whether or not
undelete keeps accounts; its addresses stay reserved and its holds name
it from then on. Destroy-now refuses it, and its DestroyAccount task
defers itself while it's held or its time hasn't come. Holds placed or
released later freeze or free kept accounts in the same settle pass,
with 30 days' grace after the last release (LH-8, LH-10).