Various blocks don't display their metadata in the F3 screen

Comparators only show their internal damage value, not the values of their specific attributes (direction, subtraction, or whether or not they are powered)

Blocks with facing values (including hoppers and end portal frames)

Flowers

Quartz

Anvils

Buttons

Beds

Rail (facing and whether or not they are powered)

Leaves

Slabs

Wool and hardened clay and carpets

Nether portal blocks

Standing signs and torches