Hi Jose, like moderators in forums when you have enough karma you are allowed to edit other users questions and answers. It's with the idea that users can maintain it without much help from Atlassian.
In my opinion I think it's great. I myself have sometimes changed some to get more clear Q&A.
It can be very useful to convert comments to answers when a comment is truly deserving of being an answer. It is a bit counter-intuitive though - often the conversion breaks the flow of a conversation, which makes it less useful, because you can get a bit of a disjointed explanation of something. When I convert comments to answers, I try to judge if it might be confusing and add a "I converted this from..." type comment to explain where it came from if I think it might be confusing. It is often useful to convert answers to comments as well. I see a lot of answers that are repeats of answers already given (which is unfair on the original poster if the newer answer is accepted first). There are a lot of answers that are clearly follow-ups to existing answers and so should also be comments. I see the odd answer which is frankly wrong, but I really don't think it's right to remove these, even when I can - it's better to convert them to comments and then explain why. More people learn that way. In both of the cases above, it's mostly because people aren't sure when they should answer and when they should comment. Or don't even know that there is a difference. I'm less certain about the ability to edit other people's comments. It feels like it could be censorship, and could easily be political or manipulative, so I avoid it. I don't feel right doing it, and when I do edit a question or comment, I keep it minimal and I only do it for clarity, and I tend to comment to explain why I did it. Unless it's questionably spam, or it's my own posting (and the edit won't affect any following comments/answers)