In the above Image edit was suggested by unknown user. That edit seems to be not spam and related to user Question. But I dont know whether OP has tried this or not because It was posted with unknown user name.
what I am thinking is , how about one more option that asking the editer as " are you the original user who posted the Question " ?
- so that we can believe that the user tried this also with out any doubt on the editor and The answers can be more effective.
- what if spam posted and clicked as original user ?
- what ever the edit it is should come across the Review/ Suggested Edits. So we usually catch it and going to remove it.
Just a Suggestion ,decision is yours.