That is your texture pack not correctly updated to 1.8.
Next to the difficulty button SHOULD be a 'Lock' icon which is a new feature in version 1.8 which allows you to lock a world's difficulty.
If you switch back to the default texture pack you should be able to see it.
When you stop to eat, the block break remains and then when you punch the block, it continues (DOES NOT RESET). Does that make more sense to you?
In previous versions, you were able to eat and break at the same time.
Nice find! I tested this with a sword too and it does the same thing, I updated issue to include sword. Thanks.