Like other SE sites, edits to posts here on Chess must be at least six characters. However, if somebody makes a one-character typo in the moves of a game, the PGN parser gets stuck and the whole game might as well not be there. The six-character requirement means that this typo can't be corrected without also making some other probably spurious change. In practice, one can add an HTML comment to the post, which adds characters without affecting the appearance. (I just did this in an edit; in fact, there were three one-character errors in the scoresheet.)
I think it would be useful if the 6-character limit were removed.