Which action does not result in a penalty under the rules of golf?

Removing a loose impediment does not result in a penalty under the rules of golf because players are permitted to do so at any time prior to their stroke, as long as it does not interfere with another player's shot or alter the playing conditions significantly. Loose impediments include natural objects like twigs, leaves, or stones that can be moved without the use of tools. This action is encouraged as it helps maintain the condition of the course and makes play easier, aligning with the spirit of the game.

In contrast, improving a lie with tools, changing the condition of a green, and moving a non-movable obstruction are all actions that either violate the rules or can lead to penalties, as they could unfairly alter the course or affect the play of the game.