I agree, as long as the bunny is in good health, they can be neutered. The issue is really how good are the chances that the bunny can be put under anesthesia and go through surgery with minimal risk of complication.
I wouldn't have a rabbit over 10 neutered
No really, like others have said older bunnies should be assessed more carefully (better to do pre-op bloodwork) but can still be fine candidates for sterilization. TBH if an unaltered female of any age came across my path I'd look into getting her fixed due to the higher incidence of problems with the uterus in older bunnies. That might mean getting her abdomen ultrasounded prior to slicing and dicing, though.