I use em, and have mounted em to 'peds that did not have em on there when built, not that anyone really pays attention to them, but in heavy traffic situations...since the horn of a Tomos sounds like a somewhat pathetic duck call, I've taken to carrying a whistle on a lanyard.
I want over, I do signal, but moped signals are not really bright enough to be fully visible during the day, so I pull nearby, and blow the whistle, and point to the lane I am moving to...and if he don't like it, he gets a few more signals of less polite type.
As for left turns, now...one thing that drives me tack-spitting pissed in a heartbeat....I got mangled during a left turn specifically, it is quite literally the most dangerous highway manuver with a moped that there is.
First you have to cross multiple lanes of traffic, usually, to GET to the turn lane, and then you have to wait till you have a gap large enough to get through with the mopeds lesser accelleration...and while the light is green.
You could pull out into the intersection, and wait till it goes yellow and everyone stops, sure...but I damn near got killed that way, by someone hitting the gas and blasting through when they saw the light changing.
And that brings me to this.....
The guy sitting on yer ass, hammering his horn, cause HE thinks that gap is big enough to turn through, when you know it is not....and mind, those oncoming folks have the right of way, and with the selfish, impatient attituds of this day and age, do not depend on them slowing down to ensure you can get out of the intersection.
Anyhow, I have a policy for this situation.
If one blows his horn at me, while I am waiting to make a left, I get OFF the 'ped, with my favorite bit of chain wrapped around one fist, and go see what his damn problem is....if he doesn't run, and wishes to be agressive, I can indeed oblige him, but if he stays and chooses to bitch, I put that damn metal pegleg of mine up on his door, and look him in the eye, tell him "Last time I let some dick like you shove me into making an unsafe left....any questions ?"
There usually ain't any, and I get back on my 'ped and on my way.
Of course...and it's only happened once..if he stays buttoned up in his car and continues to honk, or threatens me with the vehicle, he loses those nice expensive sealed beam headlights and mayhaps a windshield too.
So if you find yourself behind me whilst I am making a left...you WAIT, capsice ?