I recently killed a dragon (near the loving stone) and I didn't absorb the soul. I have two theories on why this is: 1) I didn't deal the killing blow, so it's not mine to absorb or 2) there were other hostiles around so the absorb action didn't take place.
Any findings or other theories?
Best Answer
This issue should have been fixed as of Patch 1.2:
Regardless of who kills a dragon (player character or otherwise), the dragon soul will always be absorbed by the player character (spoiler: except when you currently have a particular set of Dragonborn DLC quests active). There a bug, though, regarding respawned dragons not giving up souls after death. This has been fixed by the Unofficial Skyrim Patch: