If I have a piston, a furnace, and any(?) opaque block in a row, such that the piston’s push-face touches the rear face of the furnace, then extend the piston, pushing the furnace and additional block, the furnace turns to face towards the piston. In particular, the additional block can be at least White Concrete, Sandstone, or another Furnace, but not Glass.

Before and after images

I would expect the furnace to retain the same orientation no matter how it’s moved.

Forge: 14.23.2.2618 (and .2611)
Quark: r1.4-122
FML Log: https://gist.github.com/Melvar/4b32285cbbff124ea1b0bea1a9c85217