both merges decided whether the other writer touched the account or the identity by comparing values, so a newer event saying what the row already said looked like no change at all. a deactivation repeating an older one, landing while a backfill fetched a repo marked inactive before it, lost to the fetch's active and BackfillFinished then made the repo synced. the event clocks count now too, through RepoState::account_written_since and identity_written_since, which the relay's rebase uses as well.