I just now tryed that on a test drawing and its a neat effect.
> But it takes me in the wrong direction.
> All the text indeed stayed readable, but reversed in position only, and it
> is then justified right rather than left.
> I want the mirror command to default to YES rather than NO when it asks if
> you want to delete the source object.
>
I don't use ACAD, but I d have a copy of LT97 on my machine. In LT97 it looks like you write a simple script or even a custom menu command to do what you want.