On biology stack exchange, I had reviewed a new first question and upvoted it. Then I edited it. The edit was definitely in the post body. After I edited it, I did not get the hat so about 20-30 minutes later, I un-upvoted it and upvoted it again. How come I did not get the Greeter hat then?
The question you link to in the comments is by a user who already had a previous (now deleted) post. You eventually received the hat for a different post.