A few times already I've seen users in chat complain about the willingness of reviewers to approve very minor edits whose usefulness is questionable. Sometimes the edits were even counterproductive, leading to questions that were actually off topic.
Looking at the current UI for reviewing suggested edits, the asymmetry of approval and rejection actions stands out:
To approve an edit, click a single button.
To reject an edit, click a button, select an explanation why the edit was rejected, or, if none are applicable, type an explanation.
It is much easier to approve edits — even in great numbers — than it is to reject one or a few edits. If you're going after the Proofreader badge, it's much more economical to just wave through all suggested edits.
Another problem is that it's not just easier, you don't even need to reflect about why you approve an edit at the moment: If you like the user suggesting the edit, that's good enough for the system. OTOH, when rejecting, you are forced to give a reason. You also open yourself to criticism, because your explanation for the rejection is recorded and publicly available. Others will be able to check your decisions and detect when you abuse the review system.
There is no such record of the decision-making process for approvals.
For these reason, I request that reviewers be required to select a reason for approving an edit, or type one of their own, similar to how rejection works.
This will balance the scale of approval and rejection of suggested edits. Users will be forced to think twice (as it requires two clicks) about their reasons for approval, and it will remind them what the community considers to be characteristics of good edits. Let's face it: Not every participant on this site cares that much about community consensus and Meta discussions of what is and isn't appropriate, so a gentle reminder at the time of action might be a good idea.
It will most likely not harm genuinely useful edits, and I expect that, overall, approval, being a positive action, will still be ahead anyway.
Some examples, just off the top of my head:
Significant improvements to formatting and highlighting
Significant grammar and spelling corrections (making the post actually readable)
Made post easier to find (e.g. tags, adding keywords)
Removed unnecessary or repeated content
(Hi all! So I was out taking a walk through the park on Sunday and thought about... Thanks!)
Added new information
(e.g. when content was added in a comment only, or original content by the editor)
Content corrections (if the user actually got parts of his post wrong)