Mine was off when I purchased my bike used. I'm the 3rd owner. The gentleman I got it from said it was off when he got it from the original owner. Original owner said he had stripped the mounting bolt, so he removed it completely and included a new one as a replacement.
The guy I got it from never installed it either, so I got the original dampener plus a brand new one that was never installed.
When I got the bike, installing the dampener was on my huge list of neglected maintenance. When I finally got to it, it turned out to be very easy to remove the stripped bolt so I reinstalled the original dampener. So I basically have this brand new one in the bag still as a backup.
The truth is, I didn't really notice too big of a difference. I replaced all the felt rings that stabilizes the mounting points too. Both the new and old dampener action the same and there isn't any leaks that I can tell.
I only have a tank of fuel with, and a tank of fuel without the dampener installed. The only big difference I can tell is on some rougher roads on the highway. There is more control with it, but not enough to make me worry. I'd say you would be just fine without it if you chose too. If I didn't know there was a dampener on this bike, I would have been just fine to leave it the way it was.