Turn the text into an image, then reflect it. Try directions other than LeftRight—for example, TopBottom:
When you run this code, the output is text. You can tell it’s text because you can select parts of it by dragging:
Style["fish", 40]
This output looks like text, but it’s actually an image—a picture of the text. You can tell it’s an image because when you click it, you get an orange frame. Rasterize turns text (and other things) into images:
Rasterize[Style["fish", 40]]
If you click the image and drag one of the handles to make it bigger, you can see the individual pixels:
Once you’ve turned text into an image, you can apply image operations to it. This reflects the text to turn it into mirror-writing:
ImageReflect[Rasterize[Style["my name here", 40]], Left -> Right]
ImageReflect[Rasterize[Style["my name here", 40]], Left -> Right]