I covered this in last week's newsletter but I think I've gotten MORE dupes showing up, rather than less. Please read the newsletter here for more information:
April 2017 (Polls, Hosts, Activations, and more)

The most common response has been "I didn't know," but it's been in the rules since forever, and I just mentioned it last week as well. I will be adding a comment to the Welcome PM as well.

Summary: Each member can only have one account. Multiple accounts will be merged, as has been stated in the Forum Rules. Whether a member receives a PM warning or something more will depend on their past history with duplicate accounts.