I'm playing on 1.8 client, and this bug happens on my realms server too, but before 1.8.1 came out it seemed to be fine. There is no hitbox of the rail if there is a minecart on it. This bug makes me unable to make infinite storage in compact space.

Minecarts don't stack in the inventory, but now they don't stack even in the world! What a pity!

(I'm not sure if this a bug or a new feature, but anyways it's very bad)