Q. On a shiva house, does one uncover the mirrors on Shabbos?
Why do some people remove the mirrors from the wall in the house of mourning, when the vast majority just covers them?

A. Poskim offer different reasons for the covering of the mirrors in a house of mourning.

1) Since tefilos are said on site and one should not daven in front of a mirror, as it may be seen as praying to one’s own image. (Ridvaz 1: 106, Mishna Berura 90: 71- Chelek Levy: Y.D.132). thus covering should be sufficient and on Shabbos the avelim usually attend shul.
2) Mirrors are used for personal grooming and embellishment, activities that create joy and are discouraged during avelus, when one rents his clothing, does not bathe and change garments. It is a time for introspection and soul searching. (Keser Shem Tov 1: 704, Kol Bo p. 262)). Covering should be sufficient. but this may apply even on Shabbos. (Nishmas Yisroel 10: 1: p. 216)
3) Spirits and mazikim are attracted and may be present at the mourning house. They seem to be more apt to create damage on a mirror’s reflection (Ginzei Yosef 143, Nitei Gavriel – Avelus 1:92: n. 16). Covering should be sufficient. but this may apply even on Shabbos. (Nishmas Yisroel 10: 1: p. 216)
4) A reason similar to why they used to turn the beds in an ovel’s house. It represents the marriage relationship avoided on mourning. Mirrors would carry an analogous connotation. (Droshos Chasam Sofer 2: p. 387 – Nitei Gavriel ibid.). Covering would be insufficient, as it is with the beds, but similarly it is not done on Shabbos. ( Nitei Gavriel ibid. – Nishmas Yisroel ibid.)
In practice, Horav Shlomo Miller’s Shlit”a opinion is to uncover the mirrors in honor of Shabbos, unless there is a minyan at home.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a