I think that one common theme in both works is the system of oppression that an individual must resist. Linda Brent (Harriet Jacobs) and Montag must actively combat a system of social control that dominates the individual. In Jacobs' narrative, this is slavery. It is a condition that defines one's being in the world. Jacobs recognizes that slavery seeks to remove her voice and constrict her being. Montag recognizes that the world in which he lives seeks to do the same. Jacobs articulation of a condition of freedom and Montag's resistance towards the firefighting profession are both statements of dissent and defiance towards an oppressive social order.
Both protagonists recognize that they are not able to be a part of a social order that is so actively driven by the need to silence voices. It is this journey towards liberation that is each protagonist must undertake. Both journeys are filled with physical and emotional challenges that only help to underscore the intense level of social control that is a part of each setting.