The Pernicious Revenge of Juno - by Mike Sylvia

As with the similar puzzle from 2010, the bulk of this puzzle involves sorting the statements to create logical chains linking number properties to letter properties. This time around, though, the chains seemingly break halfway through; the half-chains starting with number properties must be matched up with the half-chains ending in letter properties using well-known proverbs as links.

- People whose favorite number is 0 mod 3 have a favorite letter with no enclosed spaces (via "Beggars can't be choosers")

- People whose favorite number is 1 mod 3 have a favorite letter that is visually indistinguishable from an uppercase Greek letter (via "All work and no play makes Jack a dull boy")

- People whose favorite number is 2 mod 3 have a favorite letter that, by itself, is a vehicle registration code for a European country (via "He who hesitates is lost")

- People whose favorite number, when spelled out, has more letters in English than in Spanish have a favorite letter with at least one curved segment (via "Many hands make light work")

- People whose favorite number, when spelled out, has more letters in Spanish than in English have a favorite letter that can be found somewhere due right of the A on a standard QWERTY keyboard (via "A rolling stone gathers no moss")

- People whose favorite number, when spelled out, doesn't change length in letters between English and Spanish have a favorite letter that's a traditional letter grade in US schools (via "Out of sight, out of mind")

- People whose favorite number is an MIT course with a one-word name have a favorite letter that can't be put in front of "ULL" to produce a common English word (via "No pain, no gain")

- People whose favorite number is an MIT course with a two-word name have a favorite letter that, in the ASL finger spelling alphabet, has no non-thumb fingers pointing straight up (via "Good fences make good neighbors")

- People whose favorite number is an MIT course with a four-word name have a favorite letter that appears in the phrase "WOVEN BIRCH" (via "If you can't take the heat, get out of the kitchen.")

- People whose favorite number is an MIT course with a five-word name have a favorite letter that's a Roman numeral (via "People who live in glass houses shouldn't throw stones")

With this, you can determine for each of the possible favorite numbers from 1 to 9 what the corresponding favorite letter would have to be. For instance, 1 is 1 mod 3, doesn't change length when translated from English to Spanish, and is an MIT course with a four-word name (Civil and Environmental Engineering), so people with 1 as a favorite number have a favorite letter that looks like a Greek letter, is a letter grade, and appears in the phrase "WOVEN BIRCH". That can only be B. Repeat for the rest, and you'll spell the answer: BACKSLASH.