I will abstain from linking to specific posts or single out users, but I have noticed a definite trend in people using comments to post what amount to answers: good or bad answers, maybe, but not comments (in that they do not discuss a sub-point of the question or peripheral issues, but attempt to answer the question). This is then made worse by people using the '+1' button as a way to "vote" for said comment.
This would only be a minor problem (but a problem nonetheless) if it did not in turn lead to some questions missing a proper (approved) answer, which can be found instead in the comment. If you post a tentative answer in a comment, at the very least follow-up on it and turn it to a fully-formed answer if it receives positive attention (particularly from the OP).
Bottom-line is: don't be afraid to post real answers, and keep comments for minor points that are not bona fide answers. Thanks!