We should not be going through posts actively looking for opportunities to improve them. Rather, edits to other users' content should only be made when we spot a problem.
If you do see room for improvement that doesn't involve an actual problem (for what constitutes a "problem", see below), you should suggest the change in a comment, and invite the OP to make their own edits if they agree.
Edits to other people's posts should be reserved for:
- Grammar and spelling mistakes (be certain that they are mistakes, however... not every English-speaking culture spells words exactly the same; e.g. don't change "colour" to "color").
- Helpful formatting, such as breaking up a "wall of text" into multiple paragraphs, adding bulleted or numeric lists to existing points, or using markup to highlight or emphasize key points or sections (e.g. strategic use of bold, headers, or italics), but only if you believe the lack of such formatting makes the post actively difficult to read, or that important points may get missed by casual skimming.
- Adding or correcting links and references.
- Removing portions of content that may reasonably be deemed offensive, off-topic, irrelevant or confusing "noise", or "spammy".
- Incorporating additional information/corrections/updates/clarifications from comments.
- Tags.
If a post has multiple, significant grammar issues, re-ordering the text may be appropriate if you honestly are having difficulty parsing it as it is currently written (after any spelling/grammar changes).