[loeg]

Tl;dr they got invited to talk, the organizers didn't look to closely at the talk, and the talk was rejected or downgraded at the last minute. There is some speculation this was deliberate but I did not see it substantiated. Might have just missed it, though.

Is the blog author the same person as the tweeter? My impression is phantomderp on twitter is the blogger, but the quote tweet is another account.

[jcranmer]

It looks like the person who is resigning is not the one whose talk was rejected/downgraded, but is doing so because of the way the talk was rejected/downgraded.