If two different PlayStation Network accounts are using the same address or the same credit card do they link up somehow? Like do the accounts see that another account as matching info.
Linked for what purpose?
A master account can create sub accounts, and those sub accounts are linked to that Master account's wallet/billing info, etc.
But other than that, accounts are kept separate.
If two accounts are created, and each one is given the same address/billing information, they are still two separate accounts, and not linked in any way, except that they both have the same billing info.