What I expected to happen was that when I set off a creeper but got away quickly enough to avoid damage, the creeper's explosion would still destroy blocks.
What actually happened was...
I was trying to kill a creeper with my sword but missed so it kept walking and set off the fuse. I backed away to avoid damage and the creeper blew up. I was not hurt and did not get knockback but it did not destroy any blocks. This is a bug I have tested many times to be sure of the cause. If the player is not effected by the creeper explosion, then the explosion will not destroy blocks.
Steps to Reproduce:
1 Set off creeper
2 Back away to avoid damage
3 Do not back away enough to calm the creeper
4 Watch explosion and do not watch blocks getting destroyed.