The “suggested edit” preview is confusing

I was reviewing a suggested edit, and I noticed it was changing the code.

I then used the other preview, and this is what I have seen.

Was \only changed with \only<2->? Which of the two previews I can trust?

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This is the reason you can see the markdown view if the rendered view is confusing. The <2-> doesn't show up in the rendered before view because it's unescaped, so the browser reads it as a tag. It shows up in the after view because the edit made it part of a code block. The rendered view is generally easier to understand, but the markdown view lets you see exactly what was changed in the post source