Players will be permitted to leave the flagstick in the hole while playing a shot from the green, and there is no penalty if the ball strikes the flagstick. In the past, players had to pull the flagstick from the hole or have somebody else (a caddie or another golfer) tend and pull the flagstick before the ball struck it.
This rule was changed to help speed up play, but it might have implications beyond pace of play. For example, PGA Tour player Bryson DeChambeau has said he will leave the flagstick in the hole even on short putts because he believes the flagstick will help keep more shots from racing past the hole. There has been research by several players and students of the game, including by short-game guru Dave Pelz, that claimed players have a statistically better chance of a ball dropping into or coming to rest near the hole if the flag is left in place.
It still will be against the rules to position the flagstick in such a way as to create a perceived benefit. That is, you can’t intentionally lean the flagstick forward in the hole to try to deflect a ball downward. The flagstick still must be placed upright in the center of the hole unless a player finds that it is leaning in a certain direction when he or she arrives at the green. In that case, the player could leave the flagstick as they find it or center it in the hole.