In Spanish, it is not considered grammatically incorrect to use the subject pronoun (like "yo") with the reflexive pronoun ("me"). While the inclusion of the subject pronoun is often optional and typically omitted in everyday conversation for brevity and because the verb conjugation usually makes the subject clear, there are circumstances where including it can be useful or necessary.

Using the subject pronoun alongside the reflexive pronoun can add emphasis or clarify the subject, particularly in complex sentences or in contexts where the subject might otherwise be ambiguous. For example, in the sentence "Yo me lavo", the pronoun "yo" emphasizes that the speaker, rather than someone else, is the one performing the action.

Thus, while not always necessary, using both types of pronouns together is grammatically correct and can be stylistically appropriate depending on the context.