In fact the purpose of this post is flagging one suspicious behavior between two MSE users.
But I'll start from something seemingly non related. In the question Downvoting complete solution there was a discussion of downvotes for the question and answers in the thread Calculate the n-th term $1, -3, -7, \ldots$.
I downvoted questioner (user Ha Hi) because its question is extremely simple relative to his other questions. It is very suspicious to see a request for help in finding pattern in the sequence $1,-3,-7$ after asking help with the limit $\displaystyle\lim_{x\to a}\frac{a^{a^{x}}-{a^{x^{a}}}}{a^x-x^a}$
Also I downvoted answerer (user Madrid Zhaku) because he posted a terrible answer. Moreover he posted another terrible answer to the similar question (Find a formula for the real sequence $(a_n)$) of the same questioner. I think this is a bad practice when one user provides complete and awful solutions to homework like questions.
Then I made a small investigation.
30 of 31 question of user Ha Hi where answered by Madrit Zhaku and this answers were accepted. The only one not-answered question of Ha Hi is Find the sum $\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\dots+\frac{1}{99\cdot 100}$ also contain answer of Madrit Zhaku.
each answer of Madrit Zhaku on the questions of Ha Hi were posted on the average 5 minutes after Ha Hi asked the question. The best result of Madrit Zhaku is 2 minutes after question were posted (see thread Find the sum $\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\dots+\frac{1}{99\cdot 100}$). Also I recommend to take a look at the question Prove the formula where user commenter asked Madrit Zhaku how he managed to write such a long answer in 3 minutes.
answers of Madrit Zhaku to the question not asked by Ha Hi usually posted 2 hours later the question where asked.
User Madrit Zhaku were registered 3 month ago, user Ha Hi were registered 37 days ago. Significant increase of earning reputation by Madrit Zhaku started September 8 i.e. 33 days ago
I think Ha Hi is a fake account for earning reputation by Madrit Zhaku.