Hi,
I know there's a few questions already asking about this but I have a solution to suggest.
Issue is that when comments are emailed to a card, any images in people's email signatures are added as attachments:
I understand you want to err on the side of not stripping data to avoid data loss.
Can I suggest the following solution:

Clicking "Block" (or call it whatever you want) would delete the image, delete all identical images from other cards, and prevent all identical images from being attached in future.
Or if you're really paranoid about data loss, quarantine suspected nuisance images in a separate area so they are not shown by default but can be retrieved if necessary.
Hope that's helpful