I don't use one personally. I have never been convinced they would do any good although agree that they certainly won't do any harm.
Over the last few years I have seen 3 motorcycle accidents happen in front of me, two of those had hi-vis vests - I am not saying your more likely to have an accident in one, just the way it turned out in this case. All these accidents involved a junction, either excessive speed or the riders being badly positioned approaching it (riding near the white line quite close to the car in front). In positions like that any car wanting to pull out of the junction just can't see the bike, more of a Sorry Mate I Couldn't See You.
My opinion is you see the lights, hard reflections off the helmet etc well before the hi-vis vest especially in the dark, in fact oncoming bikes the headlight halo effects obscures all until they are quite close. I find even the large police range rovers covered in high vis yellow are not really more visible than other cars, just more distinctive. Traffic police wear hi-vis but this is more to do with them frequently having to be roadside on foot, even the ones in cars wear hi-vis jackets due to this.
Not sure about the insurance thing but I have only ever heard of police asking if the bikes had the light on, not what they were wearing.
