i think the point is good, hadwriting forces you to think more, even from typing the same.. BUT , i am unsure this would be proof you wrote it or AI genereated it , same with tatoos , AI can genereate picutres of said Tatoo...

Even though it doesn't prove the author wrote it himself, it at least proves he had to thoroughly read it before sharing.

This isn't about proof that you wrote it - it's about proof that you care. It was important enough that you spent the effort to write it out, or were so dedicated that you committed to wearing it on your body forever. It could be someone else's message, but you are proving it is important to you by showing a personal sacrifice to share the message.