Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
I get the same results, with IM v6.9.2-5 on Windows 8.1.
I have noticed this weird behaviour when I use stroke with annotate. The wider the stroke is made, the more the inside of the characters shift to the left. They shift left to the amount that makes the right-side edge of the stroke stay in the same place. It's a kind of "right-justification".
This happens only for some gravities, and the shift is always leftwards. Never rightwards or up or down. Thus, I couldn't see any reason for the behaviour.
To me, the more sensible (predictable) behaviour would be that increasing a stroke width never moves characters left, right up or down.