Ah, I see what you mean now, and I think this makes sense as to the inconsistencies in my images. When I made the multiple circles of stairs, I placed down the outer lines of stairs the same way, and I placed down the inner ring of stairs using the same method, but not probably always starting facing the same direction. I will test this again when I can and post back.
To clarify for myself and any others reading, the non-obvious behavior here is that a corner stair can exist in one of two orientations, depending on which direction it was originally placed. It will look identical in either orientation, however this "invisible" orientation will dictate which transformation style certain adjacent stairs will take on.
I'm not sure I entirely follow you, but regardless, I don't see how that explains the inconsistency. Why would some stairs turn into a corner while others, having been placed the same exact way in another location, stay straight. Take a close look at the screenshot titled stair_behavior2.png
During these tests I even made sure to face in the same directions while placing stairs (or as best I could without using command blocks to orient the player).
Still an issue in 1.8.
Still an issue in 14w32d. See attached SS.
Still exists in 14w11b. See latest screenshot.
ThePhysician2000 has the right of it. As shown in this latest attachment (using 1.8), the oak stairs were placed in a straight row, and then the stone stairs placed to complete the rings. Then the spruce stairs were placed in rows on each side of the ring.
The spruce stairs clearly follow the behavior described by ThePhysician2000.
An unfortunate but inevitable confusing effect of the way stairs transform, but most definitely not a bug.