Who can edit?
The content of this site is user generated. As such, anyone can edit it, even anonymous passerby surfers that don't even create an account.
Before you have an aneurysm at the thought that any yahoo with a keyboard can ruin your posts, understand that there's effective checks on all edits.
First, if anyone under 2000 rep makes any edit it is put through the edit review queue and not immediately made public. Users with over 2000 rep may mark it as valid or invalid. Second, users over 2000 rep generally understand the site and have proven commitment to its quality, so they may edit at will. All completed edits bump the page to the top of the active list. Everyone will see what's been edited and by who. There's no secret editing feature, sorry.
Guidelines for when edits should be made
Edits that are acceptable on all posts, whether yours or another's
- Grammar - Always acceptable.
- Spelling - Always acceptable.
- Formatting - Always acceptable if it helps break content into a more readable form.
- Tags - Always acceptable if the question is well categorized into tags you are adding in, or doesn't fit well in tags that were added by the previous revision or original post.
These are what you might call administrative edits. There's a 6-character minimum on edits, so if the only issue with a post is a missing period, you'll have you ignore it and get proper treatment for your OCD, or 'cheat' and change a word or something.
Edits on others' posts that are acceptable with the right context
- Clarity - A bit subjective, but almost always acceptable. Things like using the correct names for things, shorten complex sentences but keeping the context and meaning, etc.
- Title doesn't match the body - Sometimes it obvious which one the asker is really asking about or it's been clarified in comments. If you don't know, comment instead.
- Factual inconsistencies - Acceptable if the question does not depend on it. If the question is based on it and it is a common mistake, let an answer address it.
- Bulk removal - Some people give way too much detail in their questions. It's usually acceptable to remove it and condense the question into its main parts.
- Remove personal information or details - As you may know, pastoral advice is strictly disallowed. So if someone leaves their name, email, whatever, remove it. Also, sometimes pastoral advice can be edited to remove the personal nature of it, and be generalized into something the asker may still be interested in.
- Comments make clear what should be edited - If the asker is new to Stack Exchange and clarified in comments what he's asking, then you can make the edit yourself. It's a good idea to inform them of it comments and suggest a rollback if they don't like it.
- Get a closed question reopened - An attempt to bring a closed question to within site guidelines is an admirable cause. Make sure that the change doesn't completely break current answers. Know when this is not worth your effort; not every question needs to be resuscitated and brought back to life. This is something you will have to learn through experience.
Edits on your posts
Do whatever you want. It's your post. Just kidding. You wrote it, but it's the community's post, and the community expects you to treat it accordingly.
All edits in the previous sections are fine if its your post. You understand what you want to say better than anyone. Clear up confusion, add a point or two, fix your spelling errors, adjust the title, remove some bulk, and so on. If its a question, be very cautious of changing it in such a way that existing answers no longer answer it. That's bad. Ask a new question if it's unavoidable.
Guidelines for when edits should not be made
- Trivial changes - Things like changing words to synonyms of that word because you like that word better, or generalized pronouns changed to the other gender, etc. If it doesn't improve the post in any way, it is trivial.
- You want to change the question into something else - Even if it's your question, don't do it. Make a new question instead. Exception: the question is only a few hours old, and it's not answered yet.
- Site guidelines are laid out on this meta site, so if you are not familiar with them, don't try to fix bad questions, unless it's your own and you're learning.
- You want to bump the page to the top of the list, you dirty rep monger. But seriously, if you make the post better, then earning a few ups is just cherries.
- The question is offensive - Even if it contains hate speech or foul language, do not edit it. It's counter-intuitive, but you should downvote and flag instead. "Offensive" flags have an auto script that will remove the content if the flag count is high enough. Editing resets the flag count. Let the community work the way it should; they don't need you to protect them from swear words or hate speech.
- The question's content has become a point of contention - Take the issue to meta or just drop it and move on. You always have downvotes and comments too.
That last bullet is important especially for your context here. You are the post author, and as such you have a special insight into its intention. If an edit violates the intention of your question, change it back via the rollback feature. But if it starts to become an issue, where you and one or more people are editing back and forth, it needs to stop immediately and you all can take it to meta or just drop the issue. This is called an "edit war" and like real war, it may be important to the participants, but the rest of the community is rather aggravated by it.
The spirit of editing guidelines
The point of all editing guidelines is to help you make posts objectively better. Whenever editing, ask yourself "does this improve the post, the page, and the site?" All three must be "yes" before you try to edit. Grammar, spelling, etc accuracy are self-evidently good. Bringing posts within site guidelines is good as those guidelines have been tested and laid out on this meta site and proven to nearly always keep content at a certain level.
The rule of editing efficiency
If you decide to edit a post, edit all of its problems in one go. Search for other problems other than the one that made you decide to edit, then fix everything you catch.