reddit uses aggressive browser fingerprinting to track your alt accounts and ban. They also use some heuristics on top of that to determine similar individuals.

FYI, they go beyond IP and use browser fingerprinting to ban all your accounts.

There's also a hilarious bug in reddit logic that can let you ban innocent users this way :3

"Bob" was replaced with "Spez"

Yes it was edited. But the base image is real. It also resulted in a lawsuit.