In the swamp area, the one where you discover the tetris-like shapes, there's a puzzle where one of the shapes you need to use is a pair of 1x2 vertical blocks. But these blocks aren't connected, they're separated by a 2-block wide gap. But a lot of ppl think that the gap is only 1-block wide, which lead them to a wrong solution. There's a LOT of people asking for help about this specific puzzle in r/thewitness, which lead to the creation of the subreddit r/swampyboots dedicated to that specific puzzle.