This is not interesting in the way that "DNS parsing is turing complete" is interesting. Nobody can send you a unicode file and make you run an infinite loop or whatever.

Within Unicode is defined a DSL used internally by the library implementers to define some business logic, like most DSLs it is turing complete. Anyone with the ability to make you run their rules file already has the ability to make you run arbitrary code (it's a software vendor for software you use).

It's still always fun to find Weird Machines, but as they go, this one is not very weird (it's one of the known families of programming languages, the Mathematica language being the most well known example. The person who specified this most likely was aware that this is turing complete and it's the rules author's responsibility not to write infinite loops).