In the spoken language that first sentence can be ambiguous. It can be pronounced in three important ways; first it can be uttered with a rising intonation, which correspond to a plain question, and it must then include an interrogation point at the end when written down; as a plain question, it causes the person spoken to to suppose that the speaker is doubting their identity or does not know at it at all; it is not downright impolite, but according to the context it can be felt as not quite courteous, and the person spoken to may even feel that the speaker does not trust them. This question form is what people will use on the telephone when there is no certitude about which person is answering. People will give a confirmation in that case (Oui, je suis Mme Renaud // Elle-même, je vous écoute. // C'est moi. // (C'est) moi-même…)
For the second way of enunciating this sentence, you do not use the rising intonation, which is the mark of questions, but instead you use a normal intonation with only a slight rise (at the end), and for punctuation in the written form you can use suspension points. This type of intonation is used to formulate statements that are suppositions that the context makes likely, they are not quite questions, and they are appropriate in face to face interaction.
- Ah je vois, la machine à glace et du whiskey sur l'étagère … de temps en temps vous prenez un moment de répit …
It is this second intonation and form which is likely to be used, although there'll be people to use the question form, this being so because the difference is tenuous and/or they haven't yet realised there exists another way or even because, if they realised it, they still have to learnt it. In most cases, a confirmation or a denial follows, but the person spoken to does not always answer and a lack of a reply is taken as a sign that they assent.
Often the word « bien » is not used, and no sign is given that a confirmation is expected.
- Vous êtes l'électricien… Bonjour (repairman at the door)
There is a third intonation which consists in a normal intonation with in addition a somewhat stronger stress on "bien" and on "< name of job/quality/…>". In this case "bien" can have all sorts of connotations, from bad to good, and they depend on the word used for the job, quality, etc., and the context.
- Vous êtes bien un pacifiste. (good, obviously)
- Vous êtes bien un menteur. (bad, usually)
In my opinion, "really" is not too good a translation in this particular case. I don't see it as impolite in English, but rather as inappropriate, unless the person called Jacqueline is known to have been raised from the dead recently (to use a context blown out of proportion).
- Jacqueline, c'est (bien) vous? (meaning of "bien": "I am not in error, right?")
- Jacqueline, you are Jacqueline, right? (or better than "right", possibly: "aren't you")
You can keep "bien" in those contexts, remembering that "really" is not very exact for a translation. "Really" is perfect for sentences of the type given above as illustration of the third intonation.
Vous êtes bien un pacifiste. (good, obviously)
You really/sure are a pacifist.
Vous êtes bien un menteur. (bad, usually)
You really/sure are a lier.