Board Thread:News and Announcements/@comment-14582847-20150512171440/@comment-26325435-20150515231542

Public places, such as schools will all have the same IP, as well as hotspots. (A hotspot is essentially public Wi-Fi that anyone can access)

Another reason for matching IPs would be a VPN, so if two or more people connect via the same servers, they will have matching IPs.

This person has mentioned "Trolling" on their profile, however, saying they will not do it again, so this person being at least a few of those accounts is not impossible.