Comment by luser on Harry Potter and the Methods of Rationality discussion thread, July 2014, chapter 102 · 2015-01-16T21:54:11.283Z · LW · GW

As horcruxes were explained they are quite substantial evidence that quirrel is not voldermort.

If voldermort could use them then he would take over world in year, He would first kidnap two wizards to make copy of himself which would be loyal to him and would quickly relearn all spells and kindap four other wizards and grow exponentially.

So likely explanation is as Quirrel said personality is completely different and after first forking to quirrel decided to fight voldermort and they do not try copy himself again.