En ce miroer chascun peut lire
In this mirror(3) everyone can read
The dance is introduced by the author / authority, just as the dances in Tallinn and Basel are introduced by a preacher.
The authority was present from the start. Not only in the first printed version from 1485, but also in the manuscripts from the 15th century, although the various headlines cannot agree whether he should be called "L'acteur", "Un maistre", "Le docteur" or even "Macabre le docteur".
Many books in those days were introduced and concluded by an author/authority. Lydgate lets an auctour introduce his "The pilgrimage of the life of man": »Her be-gynneth the prologue of the auctour«. Chaucer ends (very abruptly) his "House of fame" after having introduced a »Man of Gret Auctorite«. Many contempary books show an authority at his writing desk, but what makes this particular authority special is that an angel holds a scroll with a Latin text.
After a while all of Guy Marchant's woodcuts ended up in Troyes, but not the authority. Instead the publishers in Troyes used a number of other woodcuts of an authority in front of his desk, particularly the one to the left. None of these authorities had an angel, so the angel's two lines in Latin were no longer a part of the text.
The picture to the right is from another book published by another company in Paris in 1521. Evidently this particular woodcut had been left behind in Paris. The angel's scroll has been blanked out.
There are only a few variations in the first verse. The biggest difference is in the headings: whether the authority should be called "L'acteur", "Le docteur" or "L'autheur".
Apart from this there are only divergence of spelling, but this can be interesting enough when it comes to the name of the dance itself, "La dance macabre", in line 5. The various sources vacillate between "danse" and "dance", while BL Add. 38858 calls the dance "Le danse macabre". The name vacillates between "macabre", "machabre" and "Macabrey" (with La Danse Machabray on the front page).
In the second verse there is a great variation in the 11th line. All our printed sources (with the exception of La Danse Machabray) state that he who mirrors himself in the dance is wise: »Saige est celuy qui bien si mire«, while all the manuscripts (and La Danse Machabray) regard such a person as happy: »Cilz est heureux qui bien sy mire«.
In the 12th line the cadaver is called "le mort" (the dead man). It's only in later sources (Jean Belot, Oudot and Baillieu), that the cadaver has become "la mort", Death itself.
In the 14th line Baillieu writes "tiere" instead of "fiere", but this is probably a typo.
Footnotes: (1) (2) (3) (4)
The text was reproduced in many versions - and the different source variate between "Le Mort" and "La Mort". See Death's Dance, or Line of the Dead.