Well, here is a chance for Mark to gain some street cred, if he has a mind to help Rex, and assuming Rex wants the help. We can see signs of Mark’s growing impatience in the last panel, as if Mark has an “I can fix this!” pulse quivering up the back of his neck.
Diana told Mark earlier that Rex has depression issues, so I’m thinking that if Mark interferes, it will not exactly build up Rex’s self-confidence. Just bite your tongue and stay put, Mark! Well, if this fails, there is still time for the Kaytarist of Hamelin approach.