Chess960 or Chess959?

Question

Once in 960 times, Chess960 should just be the same as regular chess. Are there any known instances of this? Or is this selection automatically excluded, after which they just roll the dice again? So is it really "Chess959"?

EDIT: Found this: https://lichess.org/forum/lichess-feedback/chess960-starting-position-518-is-like-regular-chess. An online player complains that he has faced the dreaded 518 two times. And why not? My golfing uncle hit two holes-in-1 during his career, and that’s got to be a lot less likely than 1 in a thousand!

But I think that Chess960 can’t be that popular at top levels or there would be a celebrated example where GM X faced GM Y over a 518 Game Array.

Answer 1

There is no mention of excluding the regular starting position in Appendix F. of the FIDE Laws of Chess, so it's really Chess960 and not Chess959. I can imagine that there are chess programs or websites which do exclude the regular starting position, but this is against the official rules.

Answer 2

There is a "Chess959" which advocates the removal of SP 518 (which is when the factors that lead to "randomizing" the chess pieces happen to have the same arrangement as the traditional layout.) The rationale for removal is that players have so much training in that one starting position that the game becomes less about who is the better, more reactive OTB chess player and more about who has prepared their opening lines.

Assuming both players are actively participating in Chess959 as opposed to 960, in the event of rolling SP 518, simply re-roll.

Answer 3

2019 Update:

From 'Regulations for the 2019 FIDE World Fischer Random Chess Championship', it's excluded:

If during the event the start position of classical chess is selected, the draw for the initial setup of the pieces will be done again.

Even 2022:

Also Regulations for the 2022 FIDE World Fischer Random Chess Championship

If the start position of classical chess is randomly selected, the draw for the initial position of the pieces will be repeated.

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Check out:

Chess959 not Chess960 ! See in 2019 and 2022 regulations that FIDE's World Fischer Random Chess is actually Chess959. Now can lichess please do the same?

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2024 Update:

In 2024Feb Freestyle Chess (GOAT not MTOAT I guess):

https://www.chess.com/news/view/2024-freestyle-chess-goat-challenge-day-1

the way the position is drawn using 958 balls (the normal chess position, and the same position with queens and kings swapped, are excluded)

So SP518 and gender-swapped SP518 (SP534) are out.