When shooting an arrow at a sign/hanging sign the expected result is for the arrow to hit the sign and get bogged down, but it goes through the sign instead.
How to reproduce
Start by crafting a sign or hanging sign
Then obtain a bow and some arrows
Place the sign and target the sign using your bow, it will pass through the sign.
Observation: The arrow passes through the sign.
Expectations: The arrow should interact with the sign just like any other block.
For hanging signs, refer to MC-256505 which was resolved as WAI. As for normal signs, they have no collision box either, so it's WAI.