I think a button would be more appropriate. Not everyone reads HN on a network they control and port scanning one's neighbors can lead to some unpleasant conversations.
Weirdly it's wrong for me, there's LAN IPs on the list that don't exist, and it's missing ones that do. Firefox on Ubuntu, with uBlock Origin, over WiFi.
You should also fix the copy. You have "To prevent your browser from accessing your Device Orientation use NoScript." appear twice, the second time under "Network Scan".