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.
Except it does say “from others”. Highlighting “can” just shows that this spell gives you the ability to do so. Another way of writing the text would be “The touch of your shadow wreathed hand gives you the ability to siphon life force from others”