User blog comment:Katie Liv Phars/Decay: The Theoretical Breakdown of Shigaraki Tomura's Quirk/@comment-34752936-20180311174708/@comment-34934284-20180311181233

A person could have more than one quirk. However, the consequences of such are highly debated. For instance, there is the theory that having more than one quirk would lead to the person becoming a Noumu, or becoming similar to a Noumu in demeanor. The only organisms in series so far that have more that one quirk are the Noumu and AFO, which makes sense because of the nature of their quirk.

There is also an interesting theory that if a person is quirkless, then they can recieve a foreign quirk and be completely unharmed. This theory is built on the basis that the brain of a quirk user had already comformed to the use of that quirk. A quirkless person, therefore, has the brain capacity to evolve to fit the quirk given.

A person can have two (or more) quirks, however, the price that has been shown throughout the series is quite hefty.