On second glance, I'm not sure it's blood, otherwise it would be more brown-ish. (Unless that's a very fresh print.) It's more likely to be red ink that they got off an ink sponge or something. At least, that's what I hope it is...
Are these all the same morons from flat earth, moon landing hoax, Trump would be a great President, 5g cancer or mind control or whatever it is, and jet fuel conspiracy memes? There can't be this many stupid people. It has to just be the same stupid people falling for everything every time, right?
There's often something of a progression to it, with many branching and re-connecting paths. I think sovcit winds up as the final form for some of them though, which few have the ... talents to truly attain.
Most get off somewhere between vaccines cause autism and Jews run the world.
It prevents the recipient from forwarding the letter to anyone without the sender's consent (e.g. to a court as evidence) because that would violate copyright.