My favorite is when they forget to remove the placeholder brackets.

Hello, [user]

Or like "Matt Damon" here:
https://file.nostrmedia.com/p/4eb88310d6b4ed95c6d66a395b3d3cf559b85faec8f7691dafd405a92e055d6d/af067c774a16040d67c44bd6a723ab98ca4275c9282281764fd313b6a641113e.png