English section question! need help!

Basic question about comma.

The Sargeats also established a relationship with the famous

suffragist Susan B. Anthony, who (underlined)

was jailed for registering to vote.

Why is the underlined part correct(comma after Anthony)? The rule about comma that I learned is that there should be no comma if the name or title is one of many. There should be a comma between name or title if the name or comma is only one person or thing. Moreover, there should be no comma before who (Always).

Any thoughts?