Player A has 3 life left. Player B attacks with a Dauthi Marauder that has been enchanted by Player A's Soul Link. Does player B win, or does nothing happen?
On the one hand, "whenever" makes it sound like the trigger (dealing damage) and the effect (healing damage) happen simultaneously.
On the other hand, combat damage doesn't go on the stack, while most other things do. So, possibly the combat damage is dealt, state-based actions are checked, and now it's too late for the Soul Link effect to heal player A.
If anyone knows which way is correct, my thanks!