Rising from cushions allows passing through walls, fences, and gates, but sitting down is not.

When placing cushions on walls, fences, and gates of all types, the player clips into the block upon standing up—preventing them from crouching (holding Shift)—which is a bit annoying, you know? It’s a minor bug, but it’s really irritating. Just kidding! It might actually be useful for Redstone mechanics. It is a shame, though, that you can't turn into an andesite wall by placing two of them together (I really wanted to do that).