>>213095813 (OP)It's one of those maybe subtle things. One of those things you have to pay attention to and put together to get the whole picture of the character. But Mac was different from the rest of his unit. outside of a mission he was just a clean put together dude in comparison to everyone else.
The shaving thing wasn't only a visual to show he was upset or unnerved by the loss of his friend ( the razor literally snapping) but also reinforcing that Mac was someone that took care of himself, groomed himself, valued a certain degree of order. Even in his monologue, the emphasis on how he and Blain went through this ordeal in the past without receiving a "a scratch, not a fucking scratch".
https://www.youtube.com/watch?v=yBwP4yb9jAw
https://youtu.be/2Lgs2FiHtoE?t=54
Dude shows up to work in a button up suit.