Additional comments mandatory when Incident state changes from New to In Progress

[mgraden]

I'm trying to create an onChange client script that makes the additional comments of an Incident mandatory when the state changes from New to In Progress. For some reason it doesn't work, but if I change it to 'work_notes' instead of 'comments', then it works. Could something be causing a conflict? 

Also, we have an onLoad client script that switches the state from New to In Progress and make comments mandatory if the assigned to is the current user (second screenshot). This one works. Why is setting comments mandatory working in the onLoad but not in the onChange script?