How many microbans does "Zeus ate my homework" amount to?

Few enough that it's in the "barely worth mentioning" bracket, of course. (Under any kind of resource constraint, it wouldn't be mentioned at all, however that only relates to its infinitesimal weight, not the nature of what it is (evidence).)

You say that shouldn't be classified as evidence, I say it should. Note that the table is about strength of evidence.