I really can't even begin to properly explain this because it's just so many layers of intuition. No, you absolutely cannot have a line break in your name. That's not a letter. That said, I'm fully prepared for someone to give me an example of some writing system that uses line breaks for unique purposes apart from spaces.

John

Doe, related to Derrick Nippl-e perhaps? (Fry and Laurie)

Be funny as fuck if Canada started extradition procedures when he landed

John doe is invaild syntax.

It just be

(John \doe);