...dupes are not illegal simply because you can't differentiate between a genuine new user and someone who (probably) got their main account banned but still itching to post.

Dupes are so rampant that a possible new user automatically is seen as a dupe.

So again, not illegal but same rules apply.

There are dupes that purposely create new account to harass, threaten, kamikaze, etc. Those will be dealt the same way as other users. Obviously.