Rabulias
the Incomparably Shrewd and Clever
RAW citation? (And you do understand I agree with you on this?) I mean all the talk about heavily obscured areas does not mention walls....Vision doesn't go through walls unless there is a specific mention that it does.
Vision not going through walls is an a priori assumption that does not need to be RAW, IMO. Just as an ability that lets one see invisible creatures negates all advantages of invisibility with respect to that particular viewer does not need to be explicitly RAW.