While anyone with >1000 rep is allowed to freely edit any post, this privilege comes with the responsibility to ensure that your edits actually improve the post, and don't just clog up the site with noise. The Help Center page on the Edit privilege states:
Tiny, trivial edits are discouraged - try to make the post significantly better when you edit, correcting all problems that you observe.
Editing a post also bumps the question to the top of the homepage. Please be mindful of this and make your edits count, so that the new attention is brought to something substantial.
While it's good to fix problems that you see, you should make sure that:
- The edit is substantial and actually improves the question. Don't just play around with it or change the wording of something because you like it better that way.
- Try to fix every problem with the question. If you see a spelling error in an old question, don't just edit that one thing, try to improve the whole question. See if there are more typos, formatting errors, issues with tags, etc.
- Try to respect the original poster's writing style. If the change is just stylistic and a matter of opinion, don't edit it, even if you would have written it differently.
- The standards for editing a question should be higher if it's old. There's no reason to bump a 5-year old question to the top of the homepage just to fix a simple spelling error. If you're going to bring that old question up again, you really should try to improve it significantly.
Sorry if this came out as a bit of a rant, but I thought it was worth bringing up. Please post a response if you disagree with any of this.