Gash in Suspension Piston

That's not a piston. That's the stancion tube. It doesn't move. You're going to have to figure out if that gouge has penetrated into the inner wall and bulged it on the inside. If so, the slider part of the fork will be impeded and that is dangerous.

In order to check it, you should pull the spring out and slide the fork to full compression and see if there is any interference. I'm betting there is. And that would render the fork unusable from my standpoint.

Thank you, I will take the spring out and compress it to check for obstructions.

I don't think that I can edit my post but I would like to correct my inappropriate terminology.

Being that it is on the larger diameter portion of the tube you will probably not have any problem with binding against the inner stanchion, but I would seriously consider replacing it anyway and definitely be looking for additional damage like torsionally twisted triple clamps etc,

I hate to seem as ignorant as I am, but aside from visually inspection and a hand level, is there some methods that might indicate damaging torsion?

The first and easiest way to tell is if the forks slid out of the triple clamp easily or if they had to be muscled out. When all the pinch bolts are loose and the clamp is straight the forks will basically fall right out. If you have to tug or pull on the forks once the pinch bolts are loosened then that is a sign the clamp is twisted up.

They came out very easily, I am glad to report.