I think that both Dealing with answers in comments. and What should one do when one's question has been answered in the comments? are good duplicate targets for the recent question Closing a question which is answered in a comment?.

I have cast close vote with one of them as the duplicate target. Could somebody add close vote with the other one? (So that both these questions are shown in the duplicate banner.) Thanks!

[ SmokeDetector | MS ] Blacklisted username: how to find basis of a matrix subspace W of M2x2 by niggachu on math.stackexchange.com

[ SmokeDetector | MS ] Blacklisted username: how to find basis of a matrix subspace $W$ of $M_{2\\times 2}$ by niggachu on math.stackexchange.com

[ SmokeDetector | MS ] Few unique characters in answer, repeating characters in answer: Do prime numbers have prime factors? by yaaaaaaaa on math.stackexchange.com

[ SmokeDetector | MS ] All-caps answer: Find Domain of a function before Simplifying? by Chewbecca on math.stackexchange.com

[ SmokeDetector | MS ] Offensive answer detected: how to convert 1e+11 into number? by Nibbles on math.stackexchange.com

In a meta question somebody linked to this question: [How can $\sum_{n=1}^\infty \frac{1}{n}$ be simplified](math.stackexchange.com/questions/1938736/….

At the moment, it has three close votes as unclear and one off-topic. Well, perhaps, but would not closing as a duplicate of Why does the series $\sum_{n=1}^\infty\frac1n$ not converge? seem more natural?

I did not vote to close as duplciate, since by majority rule if I add a duplicate close vote, it would be closed as "unclear what you are asking".