As they replicated through the decades, some accumulated copying errors, offhand comments, and calculated innovations that helped them prevail in the competition with other chain letters.
For example, complementary testimonials developed, one exploiting perceived good luck, another exploiting perceived bad luck.
Are there any paper luck chain letters still circulating, perhaps distributed by hand?
The last one I collected was almost ten years ago, in 2008.
These innovations probably began in other languages and were translated into English.
Though I am solely responsible for the approach and presentation here, this effort was sustained because a few people expressed interest.