I dont quite follow your point - youre worried that I might have used my real email address when creating this HN account, or used the same password as a different HN account?
The same (or similar) password as any other online account you have. In theory that should be safe(r) than using the same email (obvious to most people as a key for joining data). As I said, I just saw that mentioned by Snowden in Citizenfour -- and it stuck with me, as yet another thing that could be used to track a user across accounts.
