Hummm, a popular you say? Popular trees are a soft wood, rapid growing tree. poplars are a riparian tree. They evolved next to water. If it’s planted in a dry area, it’s already stressed, so it may be dying back anyways. It’s actually to your benefit that the homeowner has stripped it out and and lionstailed it. Because of the prior (mal-pruning) the tree is already accommodating itself to reduce resources to that limb. I don’t know what area in the world you’re living in, but if the tree is in its natural area then it should be OK. Keep in mind that poplars are basically a short lived tree.
I would cut the freaking limb off and not worry about it personally. Hope this helps.