Torabi, I believe it would be more balanced if the armor does not stack. If you could stack water buckets you could place more water. Easy armor changing should come at a price, inventory space. Also, I speculate that horse armor will eventually have durability.
Torabi, the the punch destroys the leash, because the crosshair is focused on the leash, not the block. The leash receives the click, not the block, so instead of a block being placed, the leash breaks.
Megan, Yes, they do, but still, it would be nice if they could fix it. It adds to the "only a 2D skin" feel to the game. Mainly the chunk loading adds to that, and I love how they made items 3D to help get rid of that feel... But they still have some 2D objects in the game like redstone torches, wheat, carrots, potatoes, etc., redstone dust, minecart tracks, armor, ladders, fishing rod bobbers, arrows, and the particle effects... My computer is horribly lame, (20 fps with optifine, Minecraft crashes every 3 mins D'=) but I can still get the 3D items and not increase lag.