The RAW only offers one explicit way to break a stance and that is to voluntarily change to a different stance. Most people interpret this as allowing you do enter a stance once you get the feat and remain in that stance for the rest of your life (and beyond in some cases).
The definition of Stance is "the way in which someone stands, esp. when deliberately adopted". I believe this implies that any movement breaks the stance and if using a swift action to enter a stance, ends movement there. Paizo has such restrictions on word count, that it seems reasonable to use flavour text and any other wording that makes it through editing as RAW.
I'm no martial artist, but a while ago a monk using Crane Style moved all through combat triggering AoOs. I picture him doing this hopping on one foot based on the "Karate Kid" movie. I like the way they do it in "Last Airbender" (animation): Move, move, move, stance, do the thing.
Assuming movement breaks the stance, what other conditions would have the same effect? Prone. Sleep/Unconscious. Confusion. Mounted or Ridden. Medium or Heavy Load. Bound. Grappled. Some of these still allow you to enter the stance (i.e. Prone, Grappled) on your turn.
Conditions not breaking the stance: 5' step, teleports that don't require movement, Reposition, most others such as Sickened, Fatigued, etc.
Opinions?
