Hmm, yes, if the context is people who are very into mainstream life - they buy into social norms, and do not like to be different, etc.. they may look at an original personality as being a threatening or awkward or sadly lacking thing. But if you are not a suburban robot, then you would see it as a compliment, and would be horrified to discover that you are not an original personality.
I think it depends on how you phrased it. "You are an original character"is in my mind the same as "You have an original personality." But if you phrased it as "You have an original character," then I think it would sound unnatural. It would be appropriate e.g. in a situation where someone said: "You have an original character for a husband."
Perhaps not everyone knows that "persona" was the name given by the Latins to the wooden mask used in the Greek theatre to represent the character of the different actors and to amplify their voices. In fact "persona", and consequently the derivatives like "personalità", comes from per (through) sonàre (to sound).
It is not very usual, in British society, to refer to another persons personality. It is much more usual, especially in conversation, to refer to a persons character (which is given herein as the proper first alternative to the more clumsy, in this context, personality). Idiomatic speech is not necessarily the same as textbook speech, and this is such a case.
Why not just say they have an interesting personality and be done with it?