Originally posted by [yoda](http://meta.stackoverflow.com/users/160166/yoda) on [Meta Stack Overflow](http://meta.stackoverflow.com/a/118694/155826):
----
The following is a slight modification of [my post on meta.gardening](http://meta.gardening.stackexchange.com/questions/201/when-should-i-post-an-answer-and-when-should-i-post-a-comment/202#202). Consider a hypothetical question:
> **How can I foo the bar in X?** <br>
I'm trying to foo the bar using qux. However, I get an error message `<error>`. What am I doing incorrectly?
###When should I post a comment and when should I post an answer?
<pre>
If your response is: then it should be: Corrective action Flag as NaA
1 Can you post your comment on the If you wrote an Yes
code? question answer, delete it
and leave a comment
instead. If you
don't have 50 rep,
please wait until
you do.
2 Have you fooed the baz? " " Yes
3 What version of X are " " Yes
you using?
4 I've had the same " " Yes
problem since
version X.1
5 You missed a comma, " Vote to close as Yes
which is causing too localized.
the error
6 This was discussed in " Vote to close as Yes
this question and answer duplicate.
[internal link]
</pre>
<pre>
7 The accepted answer comment on the Write a better answer Depends
is incorrect or no answer of your own or notify
longer accurate. the answerer.
</pre>
<pre>
8 You cannot do that an answer Link to documentation No
in X because it if possible.
doesn't support Y.
9 This is what you're " " No
doing incorrectly.
[Explain]. Here's how it
should be done [code]
10 Try this: [code] " Improve the answer. No
Explain why you think
that's the solution.
If it's a code only
answer, use comments to explain.
11 This is the problem: " If it's an external No
[Explain]. In a link, it helps to
related answer/blog document the key points
post, I/they discuss here so that the crux
blah [link] which might of the post is available
be of interest even if the link goes down.
Do it yourself or leave
a comment for the OP.
</pre>
<pre>
12 See here: be heavily The answer must be Depends
[external link] improved improved as described
above, else it will be deleted.
Downvote if link is tangential to
the question. Write a new answer
with details and then flag as
Not an Answer.
Also flag if the link is broken.
</pre>
<pre>
13 I've tried these a new question If you have +75 rep, Yes
solutions and it consider placing a bounty
doesn't work on to seek a better answer.
[operating system]. If not (or if it's
How should I modify the different enough),
solution to make it work? ask a new question.
</pre>
<pre>
14 Thanks man, deleted Glad it worked, but Yes
this worked!!1! seriously, just
upvote it if you have
the reputation.
</pre>
<pre>
15 Sir, I am having a deleted with Do not encourage these Yes
similar project extreme users to ask new questions -
this is due prejudice they're most likely
tomorrow. Can you going to be closed.
please send me the code
for your project at [email]
</pre>
###Why should they be that way?
The first three responses are clearly asking for more information and don't answer the question. Fourth is merely a "me too" statement – adds nothing of value. If the only problem with the code is OP's clumsiness or if it's a dupe, they should be closed as "Too localized" or "Exact duplicate" respectively. If the former, the question should also be deleted (either by a mod or by 10k+ users). While #7 is helpful, it still doesn't answer the _question_. It is good practice to let the OP know that things have changed. If they don't respond, downvote and either move on or write a better answer if you know.
Responses #8,9 and 11 are what we'd like to see on this site. They are to the point, precise and informative. If you're referencing an earlier answer (could also be an external link), provide a crucial summary so as to make the answer self sufficient. This is important for two reasons: having the summary helps in the case of link rot (i.e., external links are dead because their site shut down) and to not have to make people click through a whole bunch of links just to get to the answer. They can proceed if they like what they see. It always helps to link to the relevant documentation/authoritative sources (quoting the important information) in your answers. Remember, in all these cases, you should cite the source(s) that you quoted (it is a good practice to make it explicit that you're quoting yourself). Feel free to edit them in an answer (not yours) if the OP hasn't done so, for after all, this is a collaboratively edited site.
Responses #10 and #12 are curt, and perhaps the most contentious of all. These are quite tricky as they do in fact answer the question, but not in a way that is considered a good answer. Moderators and frequent users generally try to encourage these users to expand on them or quote relevant parts. True, it is tempting to just leave a link and walk off as in #12. However, remember that the answers that you're leaving are not just for the person who asked the question, but for practically anyone who visits that page. If you're not willing do that, then it probably is a good idea to not post that link in the first place. #10, while technically the solution to the question, gives no indication or explanation as to _why_ that is the solution. Beyond this, there is nothing much that can be done other than let the votes speak for itself. However, if you flag these as "Not an answer", you better be prepared for a loss in flag-weight. The only time it's acceptable to bring these to a moderator's attention is if the link is dead and there's nothing to indicate what might've been there.
Responses #13–15 are self explanatory, but please, do not encourage users who post #15 to ask questions here.
###Why was my answer converted to a comment and why was I encouraged to post my comment as an answer?
Often when your responses belong to #1-#7, they don't answer the question and the moderators move the answer to the comments, where they belong (till the OP responds/updates their question). At times, when the answer is good, but falls a little short of being a great answer, moderators might nudge you to improve on certain sections or provide a little more info on the topic.
As for why answers/good info in comments is a bad idea, see [this post by Robert Cartaino](http://meta.gardening.stackexchange.com/a/218/109):
> Comments were designed to simply ask for clarification about the
> original question. Comments are such a light-weight mechanism, that
> putting *useful* information in there can actually be somewhat
> harmful:
>
> - Comments cannot be properly vetted (voted on for correctness).
> - The information in comments is not editable by the community.
> - Comments are not easily searchable. When users are looking for your content, they are less likely to come here to find it.
> - When users see that a question has been answered in comments, they are less likely to contribute proper answers.
> - Questions with comment-based answers remain marked as "unanswered" by the system, so that does not bode well for the community.
>
> When someone asks a question, members of the community are supposed to
> propose answers. Others vote on those answers so, very quickly, the
> answers with the most votes rise to the top. You don’t have to read
> through a lot of discussion to find the best answer.
> **Answers-as-comments breaks that entire structure.**
>
> Discussions in comments are no better than any bulletin board system
> on the Internet. Every time a new user comes along, they have to read
> through the initial post, then all the noise in the comments to get
> the whole story. You end up with valuable bits of the solution
> scattered among a bunch of noise and conversation. That's a condition
> we work very hard to prevent on these sites: [**The Chat Room/Forum
> Problem**](http://scobleizer.com/2009/11/02/the-chat-roomforum-problem-an-apology-to-technosailor/).
###Ok great! So when should I use chat?
If you need to have extended discussions with the OP in order to get things clarified or to work out a solution, then you should consider using the chat instead of a back-n-forth in the comments. This way you can talk to your heart's content and still leave the question clutter free. You can also collaboratively work on an answer before writing it up.
Chat is an informal environment where pretty much anything is allowed and the only moderation done is for spam and offensive content. You can discuss off-topic questions, alternate endings for the Star Wars trilogy or exchange pleasantries.
Hope this little guide helped clear some of the confusion that has been floating around on this topic.