Could, for instance, Harry split his soul into its separate agents without the act of murder? Or is the important part of the Horcrux magic stealing someone's soul to use as media to make a copy your own soul? How close are Harry's suppositions in Ch20 to the MOR-reality?
Evidence for a 'soul' and the need to eliminate another in order to do horcrux like magic gives some credence to theories that MoR is in a simulated world. You need to wipe out an existing virtual machine in order to put an extra instance of yours there, splitting your own may require dividing your 'soul/computational resources' between multiple instances, etc.
How do we know that one needs to eliminate another soul in order to do horcrux-like magic?
If copies require wiping out of existing virtual machines, population growth should be impossible. Since, at least in the muggle world, population growth happens, would this be evidence against a theory of a simulated world?
Also, if the Bacon Diary is a "very recent" Horcrux, wouldn't that imply the cost to the original is not a strict division?
[Update: and now there's a fifth discussion thread, which you should probably use in preference to this one. Later update: and a sixth -- in the discussion section, which is where these threads are living for now on. Also: tag for HP threads in the main section, and tag for HP threads in the discussion section.]
The third discussion thread is above 500 comments now, just like the others, so it's time for a new one. Predecessors: one, two, three. For anyone who's been on Mars and doesn't know what this is about: it's Eliezer's remarkable Harry Potter fanfic.
Spoiler warning and helpful suggestion (copied from those in the earlier threads):
Spoiler Warning: this thread contains unrot13'd spoilers for Harry Potter and the Methods of Rationality up to the current chapter and for the original Harry Potter series. Please continue to use rot13 for spoilers to other works of fiction, or if you have insider knowledge of future chapters of Harry Potter and the Methods of Rationality.
A suggestion: mention at the top of your comment which chapter you're commenting on, or what chapter you're up to, so that people can understand the context of your comment even after more chapters have been posted. This can also help people avoid reading spoilers for a new chapter before they realize that there is a new chapter.