Two addresses are spend-linked if they can be identified as having held coins that are under the control of a single agent. The most obvious case of spend-linking is when two coins at different addresses are spent in the same transaction, but I also identify other addresses as spend-linked if they have been used in very specific types of transactions that demonstrate no ownership change. Generally speaking, if you control the private keys to the addresses and you have actively used those addresses, they're probably already spend-linked in some form.

I also use a personal "secret sauce" to identify "degrees of separation" address ownership obfuscation techniques. You needn't worry about the details (indeed, they only reveal cheaters if kept secret) but know that if you are trying to cheat, you will get caught; and the longer you try to cheat, the worse the results will be when you are caught.

If you are not trying to cheat a signature campaign, none of this matters to you. I shouldn't have to define "cheating" and the fact that I am being expected to speaks volumes.