"Empty post discarded" means that the post did not contain any information - nothing, so since there was no information conveyed we cancelled the operation (meaning we didn't complete the requested action, and the post is gone).
Post to Facebook cancelled because of multi-network access permission conflict.
This one is actually very complicated, and we cannot easily explain what happened in a way that most people can understand. Instead I created an error message that is unlike any other, so that somebody looking for this message in the code will stumble across the full explanation. Obviously this will be lost in translation, since only the English text is in the code.
It goes like this -
// One or more FB folks were denied access but nobody on FB was specifically allowed access.
// This might cause the post to be open to public on Facebook, but only to selected members
// on another network. Since this could potentially leak a post to somebody who was denied,
// we will skip posting it to Facebook with a slightly vague but relevant message that will
// hopefully lead somebody to this code comment for a better explanation of what went wrong.