According to the help center, the purpose of comments is:
•Request clarification from the author;
•Leave constructive criticism
that guides the author in improving the post;
•Add relevant but minor
or transient information to a post (e.g. a link to a related question,
or an alert to the author that the question has been updated).
(emphasis present in source)
Any comments which do not or no longer fulfill these three purposes are subject to deletion. All users are encouraged to flag such comments as "no longer needed".
The same article also provides a list of situations when Comments should not be posted:
Comments are not recommended for any of the following:
•Suggesting corrections that don't fundamentally change the meaning of
the post; instead, make or suggest an edit;
•Answering a question or providing an alternate solution to an
existing answer; instead, post an actual answer (or edit to expand an
•Compliments which do not add new information ("+1, great answer!");
instead, up-vote it and pay it forward;
•Criticisms which do not add anything constructive ("-1, see previous
comments you scallywag!"); instead, down-vote (and provide or up-vote
a better answer if appropriate);
•Secondary discussion or debating a controversial point; please use
•Discussion of community behavior or site policies; please use meta
The points 2 and 5 are relevant in this case.
Comments are not meant to answer questions. That's what answers are for. If you would like to answer the question, please post a real answer which adheres to our quality standards. One reason for this rule is that some users (I don't want to accuse the author of this meta-question to be one of them) abuse the fact that comments can be upvoted but not downvoted. That allows them to post bad answers as comments without fear of reprisal. We generally don't want any bad content on this website, no matter in what form it is posted.
Also, comments are not meant to post opinions about the subject matter of the question. We are a question&answer website, not a discussion forum. We don't want opinionated political discussions to distract from our content. So please don't use comments for posting your personal opinions and/or engaging in political debates. (Note that if you would like to engage in debates with other community members, you can use our chatrooms).