Most of us are (or should be) familiar with this section of the Help Center Page How do I write a good answer?:
What goes into an answer
Every answer must make at least one insightful observation about the code in the question. 1
as well as this section of Why and how are some answers deleted?:
Answers that do not fundamentally answer the question may be removed. This includes answers that are:
- commentary on the question or other answers2
should be converted to a comment on the answer, since this isn't really a review of the OPs code
I didn't comment on the answer until after flagging it. Maybe it wasn't obvious that the answer in question didn't relate to the OPs code.
Was my explanation not sufficient? Should I have left my comment on that answer before flagging it? Or is it acceptable to have an answer that merely comments on another answer?