First things first:
The Commandblock will, when activated, clone the redstone repeater one block below it one block behind it.
When you place a redstone torch right on top of the redstone block, the torch will be active for exactly one tick.
I am currently playing on 14w28b, it's my latest version, but I couldn't select it above.
UPDATE: It's still a problem in 14w29b!
UPDATE: It's still a problem in 1.8.2-pre1

1.) What I expected to see:
Obviously, the command block will replace the repeater behind it. This happens in one tick, and the torch turns off. There is no more signal coming in and nothing else should happen.

2.)What actually happened:
The repeaters (yes plural - they are constantly being cloned, you can prove that easily by changing the delay of one of the 2 repeaters) are blinking like they are crazy, even though there is no signal coming in. You can remove both the redstone block and the torch, but nothing changes.

3.) Steps to reproduce:
Just build this contraption, place the torch on top of the redstone block and watch carefully