MysteryMachine expects to be used in conjunction with version control.
A commit is a version control action which records the current state of System . It is nomal to associate a comment with a commit so co-writers no what you where working on when you made a change. The idea behind that is if they don't like a change to specific Attribute they can look at the comment, and the large changes you made at the same time which will help them understand why you made the change.
Of course they still might not agree, but it should help alleviate some confusion.