My personal experience about a 1/2 hour ago.
I did wonder about should I or shouldn't I, well my recommendation is DON'T!
I did foil mine today for the first time and the grill did exactly what they warned about, I had a grease fire. Luckily I was able to contain it fairly quickly, only because I was keeping a close eye for a fire. I first had a couple of flame ups that I could blow out. Then it just lit up and spread quickly across the grill. I hurried up and closed the lid to minimize oxygen and then turned the controls off. I was thinking I should have made a water bottle but remembered we have a short hose with a nozzle hooked up to a faucet for watering plants on the patio and grabbed that. I turned it on and opened the lid sprayed a little at the base of the fire, just a couple of quick squirts. It seemed to flare up worse at first but it went out after a couple more quick squirts from the nozzle. Then I closed the lid again for a little while, a minute or so. If you put too much water on a fire in a grill and you cool things off to quick it can warp all of the hot metal. I still haven't been able to really check mine yet because it's still cooling off.
Believe me the foil is coming off and hopefully I have no damage.
A couple of other points of info to pass on, I wrapped the foil tight around the broil pan and made sure that the foil was tucked down in grease runoffs on both sides. During the cook I was keeping an eye on the grease and I didn't see the normal flow to the bucket, the grease seemed to stick to the foil instead and I was cooking at 450 - 475 degrees so there was no reason why the grease wouldn't flow to the bucket end. Also it sure seemed like the grill wasn't getting as hot at the grates because of the foil.
Incase some was wondering, I cooked a steak and some vegetables for fajitas later and then cooked some hamburgers. The grease started collecting from the steak and the fire started when I flipped a couple of those hamburgers.
I wouldn't do it. If you get away with it today and tomorrow, sooner or later you will have a fire as well.