I'm not a Go player so I don't really know how it works in practice, but what you are saying seems to disagree with the wording in Wikipedia, so I'm curious which one is correct?

You say:

> if you forget that a particular board layout may have come up in the past, go players will not note that you've messed up the game. It doesn't matter. The ko rule isn't there to stop you from repeating a board twice.

Wikipedia says:

> Rule 8. A play is illegal if it would have the effect (after all steps of the play have been completed) of creating a position that has occurred previously in the game.

> Consequence (ko rule). One may not play in such a way as to recreate the board position following one's previous move.

> While its purpose is similar to that of the threefold repetition rule of Western chess, it differs from it significantly in nature; the superko rule bans moves that would cause repetition, whereas Western chess allows such moves as one method of forcing a draw.

To me that sounds like you do need to track this, in both chess and in Go, though for different reasons (to force a draw vs to prevent an illegal move). Is this not enforced in practice?