I discovered a graphical glitch regarding block hitting with a sword and breaking blocks: If you start breaking a block with a sword, hold the blocking mouse button (Right MButton in my case), release the block breaking mouse button (Left MButton) and then start holding it again, you can block with your sword while breaking the block. If you break the block partially and stop clicking it, the block-breaking progress indicator texture remains. It's hard to explain with words, so I'll link a GIF showing it off:
http://gyazo.com/79e063ce2be78ca1df5af6a2d715c36c