So on my last playthrough during the Great Gate part, I got to the great sigil stone and I just decided to start mashing the activate button, even after I got the great sigil stone. Then when I got into my inventory, I discovered that I had collected 2 great sigil stones. I thought this was just some glitch but on my current playthrough, I decided to try this again and found out that if you mash the activate button, you can get 2 sigil stones per gate. I don't know if anybody else knows of this so I thought I would just tell someone about it.

Hmm, I have heard of others doing this, but have not tried this myself.

That is like when you put coins in a coke machine and two cans fall out. Lol.

You can get three from the Kvatch gate, it's a widely reported glitch.

That glitch is fixed on PC by the Unofficial Patch.

I don't know what anybody would do with more than one Great Sigil Stone. It's a Quest Item, so you wouldn't be able to remove it from your inventory.