Yes, the Stack Exchange network encourages community-based edits.
In the spirit of Wikipedia and other community-edited sites, we trust users – even anonymous visitors – to edit content here. However, there are some rules though that everyone should follow.
Why should I edit a post?
The most important reasons for editing a post are:
- Fixing obvious grammar and spelling mistakes.
- Making posts easier to understand, which helps both readers and the original poster (e.g. could prevent a question from being closed or downvoted)
- Adding additional information only found in comments, so that new visitors don't have to read everything
- Embedding or re-uploading images, fixing formatting, etc.
You can find more about these guidelines here, as well as on every edit page:
What should I not do?
When you edit other's posts, you're still editing the author's content. Therefore you should never …
- Change the meaning of the original post.
- Change subtleties that normally wouldn't matter (e.g. change spelling from British to American English, introduce your own writing style).
- Add something that doesn't relate to the actual post ("I have the same problem!" or "Here's something if you're interested … ").
If you understood the rules above, it's clear that you can't just go ahead and edit an accepted answer to state something completely different. If you disagree with an existing answer, vote it down, or provide clarifying comments. Or, add your own answer.*
Who is going to review it?
While anyone can edit on the Stack Exchange network, your edits will need to be peer reviewed by others if you don't have the edit privilege yet (2,000+ reputation on designed sites, 1,000+ on beta and non-designed sites), or are not logged in. Once you earn it, you can edit posts without needing approval. Users with the privilege can also access the queue of suggested edits in order to review them.
Edits that do not comply with the rules, when suggested by users without the privilege, should be rejected, or, if they've already taken place, overridden or rolled back. Rolling back will reverse the edit and take no other action, and is useful if the edit was made in good faith, if some other edit was made to the post after the suggested edit, or if the reviewer opted to improve the edit. Overriding can only be done by the post author or a moderator, and only if no other edits were made to the post after the suggested edit; it will reverse the +2 reputation gained from the edit, and may cause the editor to be banned from suggesting edits.
Users with the edit privilege are trusted to make their own edits without needing review, but they can of course still make mistakes. Therefore, it is necessary that the community watches out for all edits and rolls back if necessary. You don't even have to search for these edits: since editing a post bumps the question to the front page, it is likely that it will be seen by others.
It is not good etiquette to reject, roll back, or override an edit that actually improved a post – this would be considered rude. If you don't like the idea of having your posts edited for clarity, spelling, etc., then this site might not be the place for you. If you roll back or reject such an edit to your post, the edit may be reinstated by a user with the edit privilege or overridden by a moderator, respectively. Repeatedly doing so may cause your post to be locked to prevent edits, and if the post is a question, it will also prevent answers, so don't do it.
* On meta sites, on posts tagged faq, it is OK to drastically edit such posts if the system or the established community consensus changes. These posts are "special" and are intended as active documentation of how the system works or what the current established community consensus is, so having the most current info in the top answer(s) is reasonable and expected. On other meta posts, however, especially those tagged discussion, the general policy above applies.