I know they are required and they are on my bike but my aged street bikes that did track and street duties were stripped of them since I don't ride at night and my arms are easier and more visible to use. My 310 does double duty and while even after a few falls I've only wrecked one am considering just pulling the signals completely and preserving them. They can get a bit in the way loading and unloading my bike in the van and never use them. In 3 seasons never been hassled. On the trail with a plate are folks hassled about not having their signals? Used to be hand signals were legit and the way one signaled.
I've had all mine off this year since Jan. I've raced it, which of course who cares, ridden a few times at Gorman where they make sure you're legit, and a few sessions at Rowher Flats which is Forest Service area and talk with the rangers regularly. I think you're more likely to get harassed by a bored cop on the way to the gas station than on the trail. As long as it's registered and meets spark arrestor and sound regs, it's all good in my experience.
I pulled mine for that Hare Scramble and them put them back on only to break one in Hood River. Cheap to replace but will put them in my box of stock parts
In the UK, the LAW is, if you have lights, then indicators must be fitted and working. BUT - and this is the good bit - if the machine is designed for off-road and can not carry a passenger, then it doesn't need indicators. And, you don't even need lights at all to be legal if you want to go the whole hog - just don't use it at night or in fog! Mike