Bruce grumbling is inherently extremely funny, and every time, Clark does his best not to show this in case it encourages him not to. Here, supressed smile is redirected out the window to his left.

Clark listens to the sound of pen scratches, glancing to catch a look at the message itself, both it and the other card. Not a glance that would net literally any information for a normalman, but fine tuning his vision to peel back layers of paper, read impressions of ink, translate letters skewed at weird angles,

well, look, everyone has a hobby. Or everyone is extremely invasive a lot, only encouraged by their two full time jobs. One of those things.

They park, and Clark snags the sealion postcard he'd lifted on their way over, along with the book of stamps. He writes his message against the deposit box, after a little hemming and hawing:

Bork Bork Bork!
Hope you are doing well. Give Shelby a hug from me. Love you & see you soon.
- Clark

"Did you want to write something?" he asks, as he hovers over where he could add Bruce in parentheses.