Author of one of the linked weird machine papers here. The use of “Turing complete” in both the ROP and the weird machine literature is both incorrect and misleading; I wrote some comments on this here: http://addxorrol.blogspot.com/2018/10/turing-completeness-we...

This does not detract from this post being a good, fun, and interesting read, but for anyone that is puzzled why “Turing complete” should imply “insecure”: It doesn’t.