An answer is an exact response to a question that genuinely provides the essential information. A comment is different from an answer. If a comment would be suitable as an answer to the question, then it should be an answer, not a comment. A comment can be added to a question.
A comment on an answer can:
Acknowledge or appreciate the answerer.
Ask for an explanation about a portion of the answer.
Objectional with and/or debate the answer.
May Recommend methods to improve the answer.
Comments should not be:
Greedy, offensive, or confrontational
If a comment would be as suitable as an answer to the question, then it must be an answer, not a comment.