Maybe I’m out of the loop. Are they bots? People just meme-ing? Perverse shut-ins? Mentally ill persons? It seems like even the most horrible posts (such as one involving the death of the image subject) will have numerous comments to the effect of “Oh, I wish it was me!”… and the most impossible and fantastic depictions have comments that claim or imply experience in a matter-of-fact way.
I think they are just extremely desperate to connect with someone who shares the fetish. Think about your average ‘normal’ porn video: you’ll find the majority of the comments addressing the people on screen as if they’ll ever actually see the comment, while ignoring the knowledge that even if the comment was read by the people on screen, they’d never actually meet or respond in anything but a manner driven by money-seeking. Those folks are so desperate they’ll throw common sense out the window.
Now look at the really niche subjects, like your stuffed and snuffed stuff. The folks commenting are going to have a different set of assumptions, namely that there are so few individuals out there that share their interest that the chances of meeting IRL are effectively zero, even in the large population we have today. Those comments are their dating profile, so to speak.