As it is right now, we cannot see the raw source of the suggested edit. There are diff views and that's useful but sometimes the changes are so subtle, the actual formatting needs to be inspected if there are some problems. Or the changes are significant (but necessary) that it is hard to ensure that the changes aren't damaging or the diffs just get in the way of looking at the changes. To further complicate things, it is difficult the even access the original source if there's a pending edit suggestion. The suggestion may be inadequate and would need to be rejected. It may even be destructive (e.g., changing the formatting too much) and improving (and marking as not helpful) would be impossible since the original revision is no longer available (easily).
There's a particular case which prompted this request. I needed to migrate an update "answer" (10k) (original suggested edit and revision history) from an unregistered user into the question (where it belongs). It is impossible to view the source of the edit so I could copy the contents. The existing views renders and removes visible content from the post so using those were not an option. I was forced to accept and wait until another person accepted the changes just to be able to get at it.
Can this view be added? It's already possible to see the source of existing posts so why shouldn't we be able to view the source of suggested edits? And this doesn't seem to be something that Greasemonkey can fix.
To be consistent, a link could be placed in between the markdown diff and permalink links. Then this view will just be a raw, side-by-side view of the original post's source and the suggestion. Here's some images for comparison sake and a mockup of what I'd hope to see.
Rendered HTML view:
And what I envision the raw source view could look like:
And this would be applied to the permanent suggestion page and the popup.