You Can Only Save One From Fire - seems about right

this is what happens when sasuke uses fire style inside a wood house.

To my knowledge, Fire Style Jutsu has never directly killed anyone outside of maybe one of the myriad of filler episodes.
It is not a running gag of any sorts, it's just that Fire Style is one of the least common elements used and all known users that have killed someone has used something else to do so.
One of the characters, Uchiha Sasuke, comes from a clan where mastery of destructive fire techniques was some kind of rite of passage, yet never used it after the early arcs and neither did any other depicted member of the Uchiha clan.