Hitting any block with any sword (diamond, iron, gold, wooden) in creative mode won't break it, i've been able to kill mobs but it wont let break/ destroy any blocks with sword, that only happens in creative mode. I don't think it's a feature, i do believe its a bug. I thought i was going to be fixed in 1.6.2 version, but i still have this bug.
Environment
OSX
Duplicate of MC-18368, please use the search function to see if your bug has already been submitted. Currently over 58% of tickets are being closed as duplicate.