Signs placed on Fences in 1.6 cannot be written on.

What I expected to happen was...:
I expected to be able to write the names and descriptions of my horses on the edge of their pen.

What actually happened was...:
The sign I placed remained blank, and the sign edit gui didn't even open. Just as if I had placed any other block. I right-clicked and it appeared, un-editable

Steps to Reproduce:
1. place a fence, not sure if this bug affects fence posts, but I noticed it when I did a long fence.
2. place a sign on the fence.
3. the sign is un-editable