There are some directives about umbrella usage. Some say can.
Some say cannot. I dunno which is which.
There are cases when someone was booking in during rainy days, he
was booked by a sergeant major.
But for me, I have personally used it in front of my DSM, and
nothing ever happened.
Also another thing to note, during a COC of our div comd, it was
raining, and I was instructed to help some big shots guest to the
waiting hall with an umbrella from their car.
So yeah... 
