I think anyone can make a post and set the funds to go to @null. That should burn the rewards. Maybe make a post and test it out. Or maybe I will :D

Just look for "Advanced settings" above the Post button when you're writing your post. Click "Advanced settings" and you'll see

click "Add account" and put in null as the account, and set the percent to 100. That will change your percent to 0, and 100% of any rewards will be sent to the null account which I'm pretty sure means the rewards get burnt.