Please post a picture of the space and of the mirror. There is no one right answer. There is the answer of wether or not it works for your kitchen and dining area.

Mirrors are about what they REFLECT. Which is why they are often used opposite a window, to amplify the light and view. What will that mirror show? Dinner prep mess? A fireplace in the family room? Diners staring at themselves?

I think it is probably fine. Traditionally, a lot of people had mirrors in their dining rooms. More modern, a lot of people have the open space of kitchen+dining room... and tend to decorate the walls of the dining room on the regular. Many have opted for a dedicated beverage or display on a wall with a mirror backer. Why not have a mirror if you love it and it works in the space?

Why not? Some high end interiors are having it.

Check out RH.

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Too large in too small a space creates too much multiplication where relaxed restful dining is the goal.

I toured a FLW house where he placed an expanse of mirror along one side of the dining table, so that people seated with their backs to the expansive window could still see the view. But I always wondered if they also see themselves, chewing.

I would rather have a blank wall than a mirror. Look for good, large format art.