I recently underwent this review audit, which consists of random text inserted at random points throughout the post and some minor, unrelated deleted text.
It was pretty easy to detect and flag as spam / vandalism. In my opinion, it was too easy.
Assuming these are generated randomly, I think some improvements could be implemented.
My favorite suggestion is an alteration to the existing insert-only vandalism audits, like the one shared above. Opt to remove original words from either or both ends of a section where spam words are inserted. This simulates a realistic attempt to alter a section of text and may cause someone to be more careful when they review.
A second, lesser, idea would be to generate new vandalism review audits with only random sections of the original text deleted and nothing new inserted. If these sorts exist, I haven't found them.