Fixed in Patch 1.47.49
Sims will be more discerning over who they decide is worth mourning when an NPC Sim passes away.
Same problem for me, but even worse. Started a fresh game for the release of Seasons with a sim living alone with the body builder career. Now that he is in the middle of his adult phase, he gets at least 1-2 Mourning moodlets stacked on him *daily* as a result of sims he's mentored at some point in his bodybuilding career dying of old age. It's getting out of hand. He spends all his free time engaged in the proper activities to shed his Mourning moodlets, but then the phone rings again and more stacks get added. Note: part of the bodybuilding career includes a daily task to mentor others in fitness activities. Mentoring builds friendships, so my sims is friends with more than half the town by career level 9. My sim should be plain suicidal by now as the +Sadness from the stacked mourning moodlets keeps mounting and overpowering any other moodlets. This is ridiculous, but somehow seems intentional.
I agree there should be some difference depending on how well the sim knew the dead one. When playing a "friend of the world"-ambition sim for example even 2 days for friends would disrupt the game. Maybe like 12 h for friends, 1 day for good friends and 2 days for close relatives that you are friends with?
