Self-Healing Network (301, etc...)
GNU-Social should respond to 301 redirects by updating remote follows, etc. This way the network could self-heal if a domain gets switched or updated. More granularly, if users (or groups) merely migrate to a new site the code could get set on the user or group, executed on this granular level as a simple setting in a profile or group admin page.
This seems possible with a standard 301 code, and would make it so that site operators would not have to maintain ownership of an old domain in order to maintain network integrity after switching to a new domain, etc.