Much like how one-way arrows should not be rendered on objects, one-way arrows should not be displayed on steel pieces either. Steel cannot be destroyed in any way, making the arrows essentially useless.
This one may be a bit trickier to fix, especially in regard to manually-placed steel areas, but I'll take a look at it tomorrow. :)
Without some major changes, I can't do much in regards to manually-placed steel areas.
However, for the next update, I've made it not render them on autosteel pieces. :)