I wrote a comment on Citing CPLEX 12.9, but it was removed.
Can somebody tell me why?
It asked for clarification, it was not offensive and, though it was rather long, did not really provide an answer to the question.
To add some color for a general question of "why a comment is deleted":
A comment can be deleted for various reasons such as:
As mentioned in this answer
The only purpose of comments is to provide feedback to a question or answer with the goal of improving it. Once this improvement has happened, the value of the comment is nil and it can be removed.
Now to answer your specific question, the contents of your comment are more or less similar to what has provided in all the other answers. So, one can say that in the context (not in isolation) your comment doesn't add any new information and can be flagged as irrelevant.