Currently “nodeinfo” is mostly used for usage statistics, I guess. But we could use it for more. There is software out there that can - but don’t need to - work with Diaspora, like Hubzilla and Friendica.
Problem is that you can add users from these systems even if they haven’t activated the Diaspora protocol.
I think it would be best if all servers who speak the Diaspora protocol (Diaspora, Friendica, Hubzilla) would publish a basic “nodeinfo” dataset including the “protocols” part.
In some further step systems could check the remote systems for compatibility with the protocol when adding a profile.
NodeInfo has been implemented in #6239 and has been released with version 0.5.3.0. You can disable some statistics (user count, post count, comment count) but NodeInfo should be always available.
@supertux88 explained in #7120 (comment) that he is planning to use NodeInfo for the federation as well so we will also rely on NodeInfo, although currently we don’t rely on it.
Yes, diaspora already exposes the needed information. And I think we can add a check in the future, to only federate to pods that support the diaspora-protocol in nodeinfo.