I'm the other user who rejected the suggested edit.
Basically everything that Run5k and especially Ramhound have said applies. It was not just a matter of not correcting all the grammatical errors in this particular case.
As a side note, suggested edits also need to be substantive. So, for example, if the only issue with a post is the typo "teh" (should have been "the"), a suggested edit to fix that will be rejected. (The underlying reason has to do with wasting reviewers' time and bumping the question to the top of the Questions Page, as explained further down.)
Once you reach 2000+ reputation, though, the rules change. As edits are no longer reviewed, trivial edits are allowed. However, as the question is still bumped, you should try to limit the trivial edits to questions with recent activity.
I think one of the problems is, that the goals/rules of reviewing are not defined very well in the help center. The term "make it significantly better" is very subjective which makes it a very bad guideline for newcomers.
You are totally and absolutely right! The rules/goals of reviewing are neither available in one specific location, nor are they clear. They are also very subjective (and understandably so for a self-moderated site).
The best advice I can give is to check your history for rejected edits and even non-unanimous approvals to learn what is acceptable. (There are differences even among the different "stacks" in the Stack Exchange network.)
The only other rules of thumb I can offer are:
- Always split a wall of text into paragraphs.
Always improve all the grammar. (If you are neither fluent in English, nor have an excellent grasp of its grammar, you are at a severe disadvantage, and it might be best not to edit any posts where grammar is more than a minor issue.)
Inlining screenshots/images should be safe even if there are no other issues to fix.
- Ditto for formatting code blocks.
- Avoid edits that just add back-tick formatting and
<kbd> HTML tags.
- If the question is clearly understandable and easy to read before editing (both very subjective, though), then any suggested edit runs the risk of being rejected.
not allowing for a small quality improvement on a proposal doesn't sound logical in the big picture. The ultimate goal is to improve quality of the questions and answers. Beside the organizational issue (that it gets bumped to the top of the list, which is a fault by design an can be changed) I don't see a reason to limit proposals to large improvements. But I could name several good reasons to allow small improvements.
You can't allow un-reviewed edits by low rep users as this would lead to a massive spam/abuse issue. With a review system, you can't allow small quality improvements as this will swamp the unpaid volunteers doing the reviews.
As for bumping edits, how are you going to distinguish between a trivial (i.e. unnecessary) edit and a minor one that nevertheless substantially improves a post thus necessitating giving it more visibility?
The simplest* solution is to bump all edits and rely on a system of checks and balances to allow/disallow edits (since it is already in place for other reasons).
*Though not necessarily the best. A better solution would be to allow editors/reviewers to optionally suppress bumping, with the reviewers being able to override the editors.