Before I went on my travels, my mail reader on my desktop at home was pretty good at correctly determining whether or not something is Junk. For some reason by the time I came back it either forgot something or all spamming techniques had suddenly changed over night. Or in other words, it was hardly ever calling anything spam. So the way to fix this seems to be to re-train it on spam in your collection, so I opened up a folder with a few hundred spam emails and hit ^a and then mark/as junk to flag it all as junk. For some reason, Thunderbird then proceeds to ignore the fact that you just told it everything in that folder is junk and goes and marks a bunch of it ‘not junk’. Lather, rinse, repeat. It would be nice if it actually believed me the first time when I clearly told it the mail was junk. We’ll see if it gets the idea now.