I am working on a project that requires people to select a username. For technical reasons, the usernames are for life, and can never be reclaimed.
A reasonable list of names to reserve (root, login, signup, etc) is here https://github.com/zimbatm/hostnames-and-usernames-to-reserve
Do you ever reserve usernames in your products? If so, what is your strategy, and why? If not, why not?