The only thing I can think of is if the balloon leader has a break line and there is a suffix with just a space. So check out the prefix and suffix boxes or turn off the break line.
Other than that, no idea.
Your right. Once looked at it the control is not there.
I have run into issues with a cap when editing the text enclosure shape (slot, circle, box, etc.....)
I use circles so I don't run into any issues.