Some dialects lack such forms as ourself, themself, that is, reflexives combining plural pronoun with singular self, rather than plural selves. As a matter of style, it is preferable, where possible, to go with forms acceptable to all readers.
It isn’t always trivial to do so, however. The self-form is obligatory for me in the following types of context (where there is a single event of hitting):
Only one of us hit ourself/*ourselves.
Only one of us hit themself/??themselves.
So, if writing inclusively, I would circumlocute here, rather than choose between a pronoun that is nonexistent in some dialects or sentence that is ungrammatical in mine.