Why not make comments on what you feel should change and let the author do it, or better yet, privately message the author and suggest. It just seems really tacky and rude to edit someone else's work with out permission.
Absolutely. It is both ethical and moral, according to the community precepts established in the Stack Exchange.
We are not a forum. We believe in improving, as a group, both questions and answers. If you take a look at our help center, editing states:
All contributions are licensed under Creative Commons, and this site is collaboratively edited, like Wikipedia. If you see something that needs improvement, click edit!
Editing is important for keeping questions and answers clear, relevant, and up-to-date. If you are not comfortable with the idea of your contributions being collaboratively edited by other trusted users, this may not be the site for you.
One of the specific provisions encouraged for editing is:
- To include additional information only found in comments, so all of the information relevant to the post is contained in one place
As comments can be deleted, it makes more sense to add the information to the question/answer. This way the extra info won't be lost, and is easier to see for other users in the future.
Furthermore, because we are not a forum we don't have a private messaging function. The closest we've got is tagging someone in a comment on the post or in the public (Google-indexed!) chat room.