“Use whom, not who.” “Don’t split your infinitives.” “Use appropriate personal pronouns when talking about yourself.”
Grammar rules are here to keep us in check, but it doesn’t mean they can’t be broken. Often you’ll see infographics listing rules like they’re gospel; stuff like, “Don’t use double negatives” or, “Know the difference between that and which”.
In reality, some grammar rules are more of a guideline than a law. When you know the rules, these can be expertly appropriated to give your speech flair and personality.