Try this:
self do: [:i | ] separatedBy: []
Ha, ok, well, score +1 again for formatting code with more spacing in it (total score: 3-1). ;-) I never noticed "block args" having the problem since I always use more spacing (and, I guess, the code in the system I've ever traced).
So the real issue appears to be related to when a colon follows a non-whitespace character, as it does in your example and in keyword-selector symbol case:
self perform: #add: with: anObject
I just saw Bobs msg did half the work finding the method.. Hmm..