It does not merit a verification of the author, when you hold their content encaged somewhere they did not approve yet. You say it's to increase registrations on Fediverse and for the brighter future, but please remember to deal with this ethically. Creator deserves to know first that your mirror (or whatever ends up being) intends to seek engagement with their piece.
Linking to original, as we both proposed, is an aftermath. Top three factors also need to be addressed if you claim fair use.
As an alternative, asking for consent and delaying repost is not a rocket science.
What about "We Fedicast"?