It's a disturbing idea for most people out there and the portrayal of the doppelganger throughout world and it’s various cultures give the idea of seeing your replica or the replica of another person a very negative connotation. It is not a good vibe.
Dark Histories. Emile Sagee. YouTube.
Britannica. Literature. Folk Literature and Fable. Doppelganger. The Editors of Encyclopaedia Britannica. 2020. https://www.britannica.com/art/doppelganger
Bustle. Life. 4 Creepy Doppelganger Myths That Will Make You Never Want to See Your Double. Nina Kahn. June 27, 2019. https://www.bustle.com/p/4-creepy-doppelganger-myths-that-will-make-you-never-want-to-see-your-double-18152038
Scalar. The History of the Double/Doppelganger. Ancient Mythological Tales on the Double/Doppelganger. https://scalar.usc.edu/works/index-2/history-of-the-double-doppelganger
Listverse. Weird Stuff. 10 Disturbing Tales of Doppelgangers. Pauli Poisuo. August 30, 2013. https://listverse.com/2013/08/30/10-disturbing-tales-of-doppelgangers/
Vice. The Time When You’re Most Likely to See Your Doppelganger. Natasha Wynarczyk. October 30, 2015. https://www.vice.com/en/article/4xkeag/the-time-when-youre-most-likely-to-see-your-doppelgnger
Liveaboutdotcom. Famous Cases of Real Doppelgangers. Humor. Paranormal and Ghosts. Stephen Wagner. September 30, 2018. https://www.liveabout.com/true-stories-of-doppelgangers-2593448
Bustle. 8 Creepy Superstitions About Doppelgangers That Will Keep You Up Tonight. Jessica Booth. October 25, 2018. https://www.bustle.com/p/8-creepy-doppelganger-superstitions-that-will-make-you-hope-you-never-meet-your-double-12273817
Reality Carnival. The Official Capras Syndrome Portal. Cliff Pickover. http://sprott.physics.wisc.edu/pickover/pc/capgras.html
Whonamedit? – A dictionary of medical eponyms. Capgras Syndrome. http://www.whonamedit.com/synd.cfm/2535.html
Bustle. Psychologists Break Down Why the Doppelgangers in ‘Us” Were so Terrifying. Lia Beck. March 27th, 2019. https://www.bustle.com/p/why-doppelgangers-like-the-ones-in-us-are-so-creepy-according-to-psychologists-16980286
Ranker. People Share Creepy Stories of Encounters with Doppelgangers. Nathan Gibson. August 9th, 2019. https://www.ranker.com/list/scary-doppelganger-stories/nathan-gibson
Ancient Origins. Doppelgangers and Curious Myths and Stories of Spirit Doubles. Joanna Gillan. April 1st, 2020. https://www.ancient-origins.net/myths-legends/doppelgangers-and-mythology-spirit-doubles-001825
Double Dialogues. Self as Other. The Doppelganger. Guy Faurholt. Aahus University. 2009. https://www.doubledialogues.com/article/self-as-other-the-doppelganger/