Some traits and a bit of the wording from the tooltip from them and my interpretation of what they mean.
"stack under his command" - ex. good army administrator
Works for all divisions in a stack if the leader is at the far left of the "stackwindow" (most senior or highest ranking).
"where the force under his command is present" - ex. patriot
Might as well be written as stack instead of force. Which would mean the same as "stack under his command"?
"as commander of a force" - ex. hothead
Might as well be written as stack instead of force. Which would mean the same as "stack under his command"?
"unit this element is in" - ex. entrencher
The commander and the units "merged" with him regardless of how many other units and leaders are in the stack.
"the force commanded by this leader" - ex. reckless
Same as "as commader of a force". Which would mean that this trait would have no effect if there is a higher ranked / more senior leader in the same stack?
Please correct me where I'm wrong.