I'm not sure if anyone else has noticed this. It isn't commented on in UESP wiki or anything. Heck, it may be something that is specific to my copy of the game. This is absolutely genuine; I'm not trying to spread false rumours. It has worked several times for me, on different Oblivion Gates, with perfect consistency.

Here's how it works (in my game, anyway). When you get to removing the sigil stone from an Oblivion Gate, look at it carefully. You will see what appears to be a core at its centre. Activate at this spot. Normally, when you activate a sigil stone once, the 'activate' hand disappears, right? Well, I've discovered that if you activate in the right place (around the middle 'core'), the 'activate' hand will remain and you can keep activating the stone to gain two additional sigil stones. If it doesn't work initially, try reloading and activating in a slightly different area of the stone, it is modestly difficult to locate the optimum area but very possible.

I am uncertain whether this would work for other people too, or if it is just weird (but nice) bug with my game. Please try it and let me know!

Edit: well, just noticed the wiki actually does note it, albeit rather unceremoniously at the bottom of the page. Damn, I thought I'd made a great discovery!

I've never heard of this bug, i'll definately try it next time, thanks!!

Is this for any specific platform? I'm still running around on the Xbox 360, and they've managed to patch quite a few things on it.

I'd love to know if this works on XBox. I finished the MQ, and am not atrting a new character yet.

it's possible i'm sure as there's still some small bugs with activators i think that have not been resolved. I'll check later on on my ps3 version (goty) and normal oblivion to see.

Only times I've ever seen this work are with the Kvatch and Great Gates. If you continue clicking the Sigil after it's been "removed," you'll get up to two more stones, each one different as I recall.

Never could get it to work when closing any other gate though.

It works on PC (although the unofficial patch fixes it), and I'd imagine it would also work on consoles. For me, there didn't seem to be any "sweet spot," it was just a glitch/exploit that was possible by continuing to activate the Sigil in those two important gates.

[edit] However, the wiki does include a couple people claiming to have received extra sigils from the Cheydinhal gate.

Hmm, it's worked for me at the Kvatch and Cheydinhal gates on this playthrough, and I'm sure it worked on some others the last time. However, it does seem that it only works on some gates - I tried to get it to work at the Leyawiin gate, without success.