Do we say "to look at yourself or your reflection in a mirror, on a shiny surface, on water, etc"?

Question

In the movie "White Chamber", the man said "Look at yourselves in the mirror." (see the script)

But many native speakers say that we have to say "Look at your reflection in the mirror, glass, marble, etc." (source)

In the dictionary

reflection

(also British English, old-fashioned reflexion)

[countable] an image in a mirror, on a shiny surface, on water, etc.

He admired his reflection in the mirror.

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I think British people may say "Look at your reflection in the mirror, etc!" and American people may say "Look at yourself in the mirror, etc!" because I remember that the Michel Jackson song "Man in the Mirror" has this line "Take a look at yourself, and then make a change" (see the Lyric).

Do we say "to look at yourself or your reflection in a mirror, etc"?

One more, we say "to look at yourself or your reflection in a mirror", but which prepositions do we use for other surfaces such as glass or marble?

Do we say "to look at yourself or your reflection on / in glass, marble, water"?

Answer 1

"Look at yourself in the mirror" etc. sounds perfectly idiomatically correct to me, as a UK English native.

Although I can see us using both forms, particularly if it was the reflection which is the main topic of conversation, as opposed to the act of mirror-gazing.

Answer 2

In your source, the advice is:

Readers are accustomed to characters seeing themselves reflected in water, glass, shiny metal, etc., but they might need a hint about how other surfaces (like marble) reflect images.

This is correct. It is normal to say "I looked at myself in the mirror." because that is what mirrors are for. But "marble" is not usually highly reflective, so if you want to emphasise this you might say "He saw his reflection in the marble" or similarly "He saw himself reflected in the marble".

The preposition is normally "in"

There is not British/American difference that I am aware of. (Ignore the spelling "reflexion" unless you happen to time travel to the 18th century)