Typical copyfraud intimidation - there's nothing to stop Eliezer from publishing commercially or as traditional print publishing, if he thinks it can be defended as fair use.

Having said that, is it not rather more difficult to back up and start protecting your IP more carefully?

IANAL, but I don't see how pre-emptive addition of parodic elements could be a bad thing - at this point it's just part of the ongoing editing process in which Eliezer has revised many passages, swapped chapters, etc. If a threat had been mailed him and then he frantically began revising it, that might be different.