Yep, I actually misread "thrashed" as "crashed".

That doesn't really change anything, however; his program was acting abnormally, and there is nothing suggesting that anyone tried to attack the problem systematically through a process of elimination and deduction.

There's just not enough information in the anecdote, and (in my opinion) everyone comes out of it looking a bit silly because of the missing pieces.

There is nothing to be learned from this anecdote that sheds any philosophical light on Scheme vs. Lisp, life at MIT, etc. We learn that Scheme has/had a function that one should not use, and that computers used to be really dinky things. So I truly don't know why Greenspun wrote down this anecdote.