While revising this I found a minor issue: Nobody would do it, but what happens if casted on a Spark?
My explanation is that, unless otherwise buffed, a Spark fulfills the death condition (0 HP) upon its first attack, and the protection counters instantly wear off instead, to prevent its death. However, immediately after the counters wear off, the HP of the Spark is still 0, so it eventually dies. Thus it is no use.
Here the point is that, in the current version, protection counters protect a creature once from any kind of death.