Users interested in reducing the backlog of Unanswered questions by upvoting helpful answers may find the following queries useful:
Thank-you comment by OP on the sole answer, without upvote or accept. This lists the answers on which OP left a thank-you comment, but neither upvoted nor accepted (despite the answer being the only one given).
Thank-you comment by OP without upvote. This is a more general query: it lists the answers on which OP left a thank-you comment, but did not upvote. (It may be one of several answers given, and it may have been accepted.)
Warning #1: the data is not real-time. If you look at the very top rows, you may find that the answers were already upvoted by another user. This is less likely if you scroll down to a random position in the table.
Warning #2: the queries do not guarantee that the answer is correct. That's still up to the voter to decide.