"Names and foreign words"
Hellman is a name - think of Lillian Hellman. Hellmann is also a name, the name of the Northeast's favorite mayonnaise. You'd think if so many people love Hellmann's mayonnaise, they'd learn how to spell the name just by looking at the label.
It's not as though they detested the sauce, never bought it, and couldn't bear to look at the jar.
One of the rare correct spellings of the name came from a commenter who preferred Duke's.