(It may be useful to read the comments to this answer before reading my question.)
Often times new users post answers when the content is really just a comment. This is understandable, as new users do not have the 50 reputation necessary to comment on someone's question and if they have something to say the only place to put it is in an answer.
When this happens, more experienced users often point this out to the new user. There is apparently a "canned response" (to use DonielF's language) that says as follows:
This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker.
The first part of this "canned response" directly addresses the issue. Namely, it points out that in order to qualify as an answer something has to actually answer the question. It also points out that new users will not be able to post comments. The links contained therein provide more information as to the nature of comments, and other related useful information.
The result of this setup is that if a new user has something to say that is not technically an answer there is no venue for them to say it. However, if they have something to say which does answer a question, they are able to answer any question they want.
This leads us to the second half of the "canned response" which seems to be either a strange non-sequitur or downright inaccurate. This clause recommends that the user provide answers that don't require clarification from the asker. If this is simply a general reminder to always incorporate as much information into an answer as possible to avoid having to later clarify, then it has nothing to do with the previous clause. It would apply to all users and has nothing to do with the difference between a comment and an answer.
If, on the other hand, it is meant to tell the user that because he cannot comment he should only post answers that won't require further comments to clarify, then it is misleading the user. Any user, no matter their reputation, can post comments to their own question and answers (and will therefore be able to provide any necessary clarification). In fact, one of the links in the "canned response" is to the privileges page, where it explicitly states:
Please note that you can always comment on your own posts, and any part of your questions.
So, what is the second half of the response actually saying, what is its purpose, and how is it relevant (specifically) to someone who posts a comment as an answer?