[moderation note: I moved this to a new topic]
This is a good question, and one we haven’t addressed yet. Our current design for the SourceCred instance system is that every SourceCred instance is a Git repository, where every point in the history contains the full cred graph.
If e.g. a Discourse were to go permanently offline, the content would disappear, but we could keep the cred graph (the record of how the content was connected), so it would be possible to retain the cred for those contributions. However, they would stop getting any future cred, since no new links would be possible.
In the future, we might imagine the community making tools to help projects back up (and potentially restore) key pieces of infrastructure. E.g. snapshot all the raw data every month and store it on Filecoin.