Identity without turning the map into a social network
A public directory has a small identity problem. Anyone can submit a name and an X handle, but asking everyone to create yet another account would change the character of justbuild.it. The map is meant to help people find each other, not become another feed.
One proof, then get out of the way
The compromise is an optional X sign-in. It verifies the handle, lets one person claim one pin and unlocks a small self-service editing page. The access token is used for a single identity request and revoked afterwards; the app keeps only the public account identity needed to connect the person to the pin.
$ auth --inspect
oauth: 2.0 + PKCE
token lifetime: one identity request
account required: no
public email: never
Where it stands
The code path is built: sign in from the submission form, claim an existing matching pin, and edit your own entry. The live X application still needs its production credentials, so the controls stay invisible until that configuration exists. The no-account submission flow continues to work either way.
That is the general product rule here: identity should solve trust and ownership, then disappear into the background.