As long as you play fairly and with EQUAL strength on both sides of the board then it is not crazy to play against yourself. I do it myself as well.
It's not crazy to play chess with yourself, we do it all the time

I play against myself with the black pieces and I win those games. Just like I win with white pieces against myself.

It's probably harder than it sounds, if one were to play oneself seriously. Has to be a draw, surely? I've never tried...is it a good way to practice? At the very least it's a certain win & that's always good news!

It is very good if you want to test a new opening before you go up against someone with that opening. It is very effective for me. I play both white and black and I am of equal strength. If I lose to black well then I lose. If I win, I win. If I draw then thats fine as well. I do it to build up strategies.

...so you approach it academically, test, solve & so on. It's an interesting idea. Surely, you would still show a 'preferred' side, a leaning 'toward'. Would you subliminaly 'allow' moves to develop? (simulations don't always go well in the field after all- they

It is true. One game, one of you, could play boldly, the other cagey. Assuming you were very honest about it, statistically, how often do you throw in the random??
When we predict our opponent's moves.