The answers to some questions, even when you know them, do take a time to be written down. While you're doing it, someone's doing the same thing and when their answers appear in the thread, you get the corresponding notifications. So, continuing your writing, you can correlate your answer. And it's really good because hardly anyone wants to be pointed out that their answer partially duplicates someone else's version.
With the comments it's absolutely different — you can't second-guess that they, appearing at the time you're answering, may contain the thought you're setting forth, or you're just about to do it. It is really frustrating to have had your answer posted and find out that what you took time and effort to create as a readable piece of work, had already appeared, without your knowing about it, in a form of a brief answer or a clearly understandable hint to it.
Everyone can understand that sometimes, there may appear a question which, as it was put, needs a bit of clarification, or the answer can be easily found on a certain resource. A brief, qualifying remark or a helpful link to a resource would be fine then, but not a short answer to the question (or to a part of it). It shouldn't appear anyplace other than in the "answer box". This is not only my personal opinion but also the proposal to be considered and provided for by the rules: No answers, direct or indirect, in comments to the questions.
What do you think about it?