[gojomo]

Ultimately your only 'protection' is your willingness to enforce your rights against unapproved uses -- which very generally includes lawsuits, legal threats, takedown notices, and public shaming campaigns.

The paid registration is unlikely to deter anyone; it might be necessary if you have to sue someone, but even then, it's the suing, not the registering, that has teeth.

But mainly, you should resign yourself to the idea that someone, somewhere, someday will copy your publicly-shared work. The copying probably won't cause you enough damage to be worth prosecuting; only if your work has large economic value, and the copying diverts some of that value from you to the pirate/plagiarist, would vigorous enforcement be cost-beneficial.