I voted to close Why is there a NVIDIA logo in the [GPU] and [GPGPU] tags? because I think it is a duplicate of another question, as pointed out by Robert Harvey in his comment.
Once I voted to close it, an automatic comment was added, even though there was already another comment pointing to the exact same question.
I don't think the second comment should have been added in this case. That is what I have normally seen happening: When somebody already commented, and added a link to the duplicated question, such as in "See also [link to question]." the automatic comment is not added.
In this case, I notice there is a slight difference between the link in the automatic comment, and the link in the existing comment: In the automatic comment, the link is
http://meta.stackexchange.com/questions/33081/should-tags-that-represent-concepts-be-sponsorable, while in the existing comment the link is
http://meta.stackexchange.com/questions/33081. This difference could explain the different behavior seen in this case; still, as the linked question in both the comments is the same, the system should detect this case.
In http://meta.stackexchange.com/questions/127210/how-to-repost-a-question the automatic link is not present because there is already a comment with a link to the duplicated question, which is How do I get attention for old, unanswered questions?
I voted to close Can I ask a question on gaming stackexchange about my own game and answer it? as duplicate of a question pointed out in a comment; also in this case, the automatic comment is not added.
In this case, the link used in the existing comment is
http://meta.stackexchange.com/questions/17463/can-i-answer-my-own-questions-even-those-where-i-knew-the-answer-before-asking, the same link the automatic comment will use.