As far as I can tell, this would only occur if the strangle does indeed miss, as in I do damage to the victim, I outright miss, or he does damage to me.

You step out of the shadows.
You creep up on a dwarven merchant and apply a firm stranglehold.
You fail to get a firm grip, and a dwarven merchant frees herself with a sharp elbow to your chest!
A dwarven merchant's elbow strike decimates you!
You trample around loudly again.
Your strangulation misses a dwarven merchant.
A dwarven merchant is in perfect health.

You step out of the shadows.
You creep up on a human merchant and apply a firm stranglehold.
Gasping for air, a human merchant struggles and barely escapes your grip!
You trample around loudly again.
Your strangulation MUTILATES a human merchant!
Your strangulation misses a human merchant.
A human merchant has a few scratches.

You creep up on the elven thief and apply a firm stranglehold.
Gasping for air, the elven thief struggles and barely escapes your grip!
The elven thief yells 'Help! someone is attacking the guild!'
You trample around loudly again.
Your strangulation mauls the elven thief.
Your strangulation misses the elven thief.
The elven thief is covered with bleeding wounds.