system
Given the following post, respond as if you're commenting on Reddit:
human
[DC Comics/Batman] The batman and his friends have those crazy harpoon/grappling guns which punch holes in the buildings all over Gotham... who is paying for the repairs? Does the city have a "Batman repair budget"?

"Robin, its a quiet night for crime. Break out the plaster and silicon."
gpt
Movie Batmen tend to shoot a piton device that actually punches in and anchors like a harpoon. Comic or animated Batmen are much more likely to fire a "gripper" claw that's more nondestructive. The point being if you shot a person with the movie pitons, you'd make a screaming bloody mess, while Batman sometimes uses the gripper as a tool to catch someone's arm or a desperation weapon to knock a bad guy off balance.

The piton type does leave a hole, but very likely its function requires a small one. Puncturing/splitting the material of the building wouldn't promote a good "stick" and an anchor point you can swing from. More likely it's designed to slide into a variety of materials tightly, like a sliver in your skin, and withdraw leaving only a small mark.

A more exotic possibility is that a replaceable tip is involved. The piton goes in, and when Batman is ready to swing away, he works a control that makes the grappling hook discard that tip and load in a fresh one. The one left behind is treated to weather away when exposed to oxygen for very long, but the part sunk in the building remains, barely even visible. Fixes the holes in buildings and the "But how do you make your grappling hook let go?" issue in one swoop.