The answer to my previous question (Does the Knight's Bladed Step require the shift to gain CA?) was based on the claim that you can shift 0 squares and still be considered to have shifted. However, the player who inspired the original post found that claim questionable, and I've been hard-pressed to disagree.
While we accept that you could simply choose not to make a shift granted by a power or feature, we couldn't find anything that explicitly allowed a 0-square shift that would still trigger other benefits you gain from shifting, such as the Knight's Bladed Step or the property on the Boots of the Fencing Master (both reprinted below). Do rules explicitly allowing a 0-square shift exist? This can be either the Shift basic action, or a power that allows shifting as part of using it, but if the rules only apply to one of these, please specify.
Benefit: After you use power strike with a heavy blade, you can immediately shift 1 square to a square adjacent to an enemy. You then gain combat advantage against that enemy until the end of your next turn.
Heroes of the Fallen Lands, pg 136
Boots of the Fencing Master
Property: When you shift, gain a +1 item bonus to AC and Reflex defense until the end of your next turn.
Adventurer's Vault, pg 127
Note: While the description of the Walk action states "The creature moves up to its speed," implying a minimum of 0, the Shift action has no similar qualifier, simply stating "The creature moves 1 square," without the "up to."