The original is famed for writing obscure but dire-sounding quatrains that are continually reinterpreted until they can be made to fit some historic outcome.
Bad poetry being even less in vogue than in Nostradamus's day, the one who "looks like Nostradamus" today spouts prose soundbites hinting at insurrection, violence and treason — and claims inspiration from other obscure but widely interpreted ancient texts.
The real Nostradamus supposedly predicted the death of kings, the burning of London and the French Revolution.
One difference is that the real Nostradamus didn't try to make his meanderings come true and didn't — as near as I can tell — incite others to do so.
All he did was write harmless ditties like this:
The pretender will rail from the fox's lair
Locked with newt and loaded with bile;
The blind shall lead the one-eyed subjects
Over the precipice as their cocks crow.
I looked it up.