Q:

Reviewers can single-handedly reject suggested edits

I recently found this on Mathematics Meta. 
The Reject and Edit can be abused to reject single-handedly. 
There are examples of edits being rejected here, here, here and here. 
Because when they select Reject and Edit, the Community user rejects the edit as a moderator. 
Is this intended? 

A:

When reviewing Suggested Edits on Stack Overflow, I commonly see edits that either introduce more problems than they fix, or don't even attempt to fix all issues with the post.  In both cases, Reject and Edit is a useful option as it allows the reviewer to correctly edit the post while also not approving a bad edit.  It can also help the edit suggester learn what makes up a good edit, and thus submit better edits in the future. 
If there was only Reject and not Reject and Edit, then the reviewer wouldn't have the chance to correctly fix up a post if they were the first reviewer. 
Additionally, even if there wasn't a Reject and Edit button, reviewers would still be able to override a suggested edit by navigating directly to the edit page.  For example, if there was an edit pending on this question, I could go directly to https://meta.stackexchange.com/posts/325591/edit and override the suggested edit with my own edit.  Getting rid of Reject and Edit wouldn't stop reviewers from replacing bad edits with good edits; it would simply make it a little harder, and probably discourage users from doing it, even if it's the best option. 
Finally, Reject and Edit can't really be abused more than editing privileges.  Yes, you could prevent editors from gaining 2 reputation per suggestion, but beyond that, you're really just editing the post and overriding a suggested edit while you do that.  That's subject to abuse just as much as it would be otherwise. 
If a user is frequently rejecting and editing good edits, it can be easily seen by navigating through their profile, and then flag for moderator attention if they have at least 15 rep.  Moderators can ban users from review, so they can manually ban the reviewer from further reviewing suggested edits for a chosen period of time. 