[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.
I think it could make a decent story. I'm not sure that it hasn't strayed too far from canon anyway.
Sngr/Fgnl Cbggre
Nsgre guvf qronpyr, Uneel trgf pncgherq naq chg va Nmxunona sbe n ovg. Ur ybfrf nyy uvf unccl zrzbevrf naq gur novyvgl gb pnfg Cngebahf (vg vf n unccl zrzbel) naq fbzr bs uvf engvbanyvgl genvavat. Ur rira sbetrgf ur vf Uneel Cbggre (ur yvxrq orvat n obl jvgu qrfgval).
Urzvbar/Dhveery/Qenpb naq gur jrnfyrlf zbhag n erfphr, jvgu Urezvbar univat yrneag cngebahf sebz Uneel'f abgr.
Uneel vf nffhzrq gb or gur qnex ybeq, ol gur nhgubevgvrf, fb vf abg fnsr ng guvf gvzr, ur jbhyq or uhagrq qbja, fb vf genafcbegrq onpx va gvzr.
Gurer ur xvyyf bss Ibyqrzbeg cebcre naq fybjyl orpbzrf Dhveery. Guvf nyfb rkcynvaf jul gur Qrzragbef unir n orrs jvgu Dhveery, ur unf gur znex bs fbzrbar jub rfpncrq Nmxnona.
Dhveery unf gb pbnpu Uneel va guvf jnl gb sbez n fgnoyr gvzr ybbc.
Abj V qba'g ernyyl guvax vg vf guvf. Ohg fgvyy vg jencf hc n ahzore bs fgenaqf. V nyfb unira'g ernq rabhtu snasvp be gur ynfg srj obbxf bs Uneel Cbggre fb zl frafr bs jung unf orra qbar be fubhyq or qbar vf abg irel fgebat.
I believe that the Dementors have a beef with Quirrell because (rot13) gur Qrzragbef ner Qrngu vapneangr naq Dhveeryy qrsvrq qrngu ol perngvat n ubepehk, abg gb zragvba qlvat naq abg fgnlvat qrnq. Gurl jnag gur cevmr gung'f orra qravrq gurz.