Rule on multiple account ownership

[Neuroprotection]

I have a friend who is considering setting up an account on this site. Unlike me they are not visually impaired, but they are fascinated by one of the conditions of the agreement. This is the prohibition of ownership of multiple accounts either when you are an active user or subject to a ban of any duration. I do not believe my friend wants to do anything mischievous, rather they just seemed puzzled as to how this prohibition could be in forced, that is how would a single user opening a second account be detected.
I do not have the answers, so I decided to ask on this thread, although I sincerely hope this information does not encourage people to defy the rules.
Does anyone have any answers and also any advice of how to put the information across to my friend.

 

[One Thousand Words]

They match your IP address.