Do you find this a sincere form of flattery or insult when someone copies your movement?

It's called mirroring and it can happen naturally.Often during flirting or when we engage with someone we are attracted to.

I’ve only ever noticed anyone copying anything about me once. After that slightly creeped out feeling passed, I figured she just hadn’t found who she was yet. I was neither flattered nor insulted.

Well, if we take that maxim of 'imitation is the sincerest form of flattery' and apply it to literature or art, it is called plagiarism and forgery!

Depends on the situation.

They call that raport but call it irritating.

If they're trying to pick pocket you then definitely not.

insult, as I am disabled, copying me is to mock me