One countermeasure could be to disallow clickable links on images. Or, in this case, the link is a reflink -- so disallow links on images when they've already been seen previously).
Also, it's the same image used in each.
So another countermeasure could be to URL and if the image has already been used in another comment that some alternate occurs ... like cost increases exponentially (?), or ??? But having to create a new image on a CDN (or imgur, in this instance) for each comment spam post would add a hurdle that would likely dissuade the spammer.
Another thing that could be done as well is to notify the product/brand being spammed. Usually they have in their Terms of Service for their affiliate program that spamming the link is not allowed, and cancel the spammer's account.
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