When placing a sign on a fence, it didn't give me the option to input text, the sign just stayed blank. Placing signs on other signs, grass, and iron bars worked as usual, although I didn't try with anything else.
Linked issues
is duplicated by 90
Comments 17

Works fine with everything (even Cobblestone walls), only signs on the side of fences lack the text input menu. That's a weird bug.
confirmed here as well... really odd bug

Interesting detail: Holding the Shift-Key when placing a sign on a fence still opens the text input menu.
Confirmed, and not just in creative mode. Well, that's weird.
You could use sneak-clicking and still edit them as usual. My bro (nyspace1) found this to and we felt it could go either way as a bug or a feature since you could quickly spam signs.
I was going to post this myself, so that means I can reproduce it. Even thought you can sneak-click it, it should still be fixed.
Yup, what Bob Joe Eisenhower said, oh and both fences, regular and nether brick
If you use shift when placing, it will work! 🙂

Signs are fixed, but there are other side effects, see MC-23384
Confirmed.