Understanding the bug
So-called “Unicode of Death,” the actual “bug” stems from the way Unicode decodes characters, causing the above string to decode to an infinitely repeating message.
What happens next is
your iPhone’s memory gets overwhelmed in the process, causing the phone to respring. You don’t even have to open the message or receive a notification, it’s an insta-respring.
Having tried it out myself, I can safely report that the bug seems to work as described above. Having texted the offending message to myself,
I immediately switched to the System Monitor app, a 99 cent download in the App Store, to check system resources.
Sure enough, I was able to watch RAM on my device go from around 400MB of free memory down to less than a hundred.