If you've noticed comment-discussions being unceremoniously deleted, there's been a lot of misuse of comments in this system. Let's see if we can nip this in the bud.
Comments are like Post-It notes
Comments are inherently disposable and not for permanent information. Comments are used primarily to leave notes to the author asking for clarification, or to point out problems, or otherwise help make a post better. Ideally, this information should be moved into the post and the comments deleted.
Comments are not for answers
Comments are not a substitute for answering questions. Comments cannot easily be searched, nor can they be edited for corrections or vetted with the community vote. There's no history, no reputation awarded, nor can they be 'accepted' as the best answer. They get little visibility but often keep users from posting proper answers because the question appears to be resolved… albeit, incorrectly. Further, those comment-answers will not bring new users to this site searching for the information. In short, you are hurting rather than helping the site, and your contribution is at great risk of being lost/deleted.
Comments are not mini chat rooms
Comment-chat sessions come in the form "Yes, same thing happened to me, let me tell you…" but they also contain random quips, anecdotes, jokes, and various side conversations inspired by the discussion. If you find yourself chatting up the situation, please stop. Our chat rooms are much better suited to this purpose — http://chat.workplace.stackexchange.com
Comments are not discussion forums
Comments are not for debates or deliberations. If you find yourself going back and forth about a post, you're doing it wrong. It's okay to express disagreement about information posted (voting goes with this), but if it becomes a conversation, stop responding and bring it to a chat room. We're building a canon of clear, concise answers in this Q&A, and we sometimes have to forgo these conversations and debates to keep that repository clean, useful, and accessible. If the question needs further discussion, bring it to a chat room. Ideally, the issue should be resolved and the information added to the post. The comments should not become part of that canon.
Too much to read? Start here.
Comments are not intended for long-term storage of important information. But that transiency doesn't mean you can use comments for random, parenthetical asides. If your comment isn't likely to change the content of the post, please do not post it for someone else to clean up. Thanks.