Once Upon a Reference Plane
Once Upon a Workplane - Seeing is Believing
Is You Is or Is You Ain't
IsReference Setting - Weak and Strong
There is a head and tail, the head is where the Reference Plane name appears. There is a difference between the Reference Planes you find in a template and the ones you create by sketching them. Check out the other posts (and the embedded video here) for more on that difference.
I created the following VIDEO to demonstrate what prompted me to make it, that mirroring a reference plane isn't a good idea. At least it isn't a good idea if you have no idea what the outcome is when you do choose to do it. The orientation of the reference plane is reversed when you use the mirror tool in addition to being copied/mirrored. If you want to control the work plane orientation then use the Copy tool instead.