the reasons for sites not appearing are indeed a mixture of the above mentioned. You then went on to mention both penalties and mistakes so its not clear why you say no and then agree with me. You said it was mentioned a hundreds of times that people not appearing was because of bugs or what you call redirect problems (actually theres more than just redirect problems thats why i term them all under bugs). The point of course is that SOME peple arent appearing for that reason, others for other reasons including real penalties, many people arent aware of which problem they have, they just no they dont appear. You seem totaly focused on one single bug, the redirect 301 problem, there are hundreds of thread mentioning other problems and reasons for appearing in serps.