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Cooking Up Contingency Plans
(i.imgur.com)
Since my polymorph meme has only garnered three downvotes so far I thought I'd offer a bit more controversial take, and see if I can manage to stir the pot a bit with this one.
If we're going strict RAW, the "from others" clause only affects life force, not HP. Spells don't do more than what they say, after all. So you can take HP from others, but not life force.
Thanks to our natural language rules we can easily interpret Life Force as a synonym for HP