Hello, there are numerous of questions on the internet that go like this:

Q: Can a website identify or ban me by my MAC address?
A: No, of course websites can't see your computer MAC address (...mumbling something about an identifiable modem MAC address, while closing the topic)

In other words, could I sign up for an account which has a 1 account policy, after I once had an account there ages ago? While using the same modem, but a different IP address.
Asking for a friend of course.

Could someone please explain?