Q:

Good suggested edit, bad edit summary. Accept or reject?

Hypothetical examples of edit summaries which announce that the edits were made in bad faith:

Edit: Improved Grammar
Summary: "I'm farming edit rep!"
Edit: Removed Salutation
Summary: "I upvoted this and my vote is locked unless this gets edited. I want to revenge-downvote this user!"
Edit: Fixed Code Block Formatting
Summary: "aksghjdcnu" - This user was lazy and just wanted to meet the 10-characters requirement.

Should one reject a valid suggested edit if it has an edit summary that describes questionable intentions? What about spam URLs in edit summaries? Is it okay to accept the edit and allow the spam to show up in the revision history as a side effect?

A:

In theory, no. If the edit is still valid, then the edit summary is not necessarily important in getting it approved.
In practice it's a different story. Your edit summary is displayed prominently at the top of the edit. If it doesn't explain at all what your edit attempts to do, is vague, or is otherwise malicious (calling people names, etc) then you're just opening yourself up to reviewers being less sure about whether your edit improves the post in situations where the change isn't so straight-forward. There are plenty of cases where the edit summary saves the edit by clarifying what exactly you're doing and why.
On the other hand: an edit summary that states something that shouldn't be done or a reviewer might not approve of normally might trigger a reviewer to not even look at your edit. What you described shouldn't be done, so it needs rejected. In this case, you may be doing yourself a great disservice by not accurately describing your edit.
If you want the best outcome, it's always a good idea to give a descriptive edit description so there is no confusion in the minds of the reviewers.

A:

If the edit is valid and helps clarify the message in the post - then it should be accepted irrespective of the edit summary. The edit itself is the crucial part and if it is done properly and clearly, the edit summary would not need to be referred to.
Some may not be able to properly articulate a summary of their edit. To reject a valid edit due to problems with the summary would be unnecessarily pedantic.

