Especially, ...
Dans l’armée de terre, le brigadier des armées du roi était un grade d'officier général, créé en 1657, intermédiaire entre celui de mestre de camp et celui de Maréchal de camp .
But, to claim that "brigadier" was a general's rank is incorrect. He was actually a superior officer (colonel or lieutenant-colonel) ranking higher than a colonel but below a general: "[Les Brigadiers] ... ne sont pas officiers généraux, mais ont le pas sur les autres colonels des régiments qui forment brigade avec le leur." (s.v. Brigadier) :
https://www.servicehistorique.sga.defense.gouv.fr/guides-aide/les-grades-dans-larmee
(But the abolishment was not, as stated in the SHD-article, a result of the Revolution)
His rank insignia:
https://gallica.bnf.fr/ark:/12148/bpt6k9744151h/f45.item.r=brigadier
https://gallica.bnf.fr/ark:/12148/bpt6k9744151h/f79.item.r=brigadier
"Le grade de brigadier des armées est supprimé en 1788, il était matérialisé par le port d'une étoile. À sa suppression en 1788, le nombre d'étoiles de ses supérieurs immédiats n'est pas modifié, ce qui explique pourquoi aujourd'hui les généraux français ont une étoile de plus à leur insigne que leurs homologues étrangers (notamment américains)".
The relevant extracts from the ordinance which mentions the abolition of the rank of Brigadier in expressis verbis:
In addition, an excerpt from an older article by Georges Dillemann ("Insignes des grades et des fonctions des officiers généraux") concerning the Brigadier (note: read "éteindre" instead of "étendre" in the fourth paragraph, an obvious misprint which says the exact opposite of what is stated in the ordinance linked above) :
In the German forum mentioned at the beginning, one of the users writes:
"... Hans-Karl hatte mich auch schon auf den Brigadier aufmerksam gemacht, der kein Dienstgrad, sondern eine Dienststellung war."
This is not quite corret. In the Ancien Régime, Brigadier was a rank ("grade" ! ) indeed, a permanent one, and not just a "position" or function. It was precisely because this arrangement did not prove successful that the rank of Brigadier was abolished. Check the above-mentioned ordinance of 1788 for the reasons. The officers who were Brigadiers were probably allowed to continue wearing their star, even if they were now only Colonels or Lieutenant-colonels (the fact that Lieutenant-colonels could also be appointed Brigadiers is mentioned in the ordinance of 1788 as one of the akwardnesses caused by the rank of Brigadier).
It was similar in the navy, but the corresponding rank - Chef de division (established in 1786) - lasted longer. As a rank, not just as a function.
In an Arrêté of 7 Thermidor an VIII (26 July 1800), officers with the rank of Chef de division are still named as holders of high functions. But even in the navy, it ultimately turned out that the rank of Chef de division made no sense, because a French naval division was an ad hoc, temporary unit, unlike a squadron or even a fleet. In order to command such units, no officers with the permanent rank of Chef de division were needed (not to mention possible disgruntlements due to ambiguities regarding the hierarchy). So the Chef de division was de facto abolished by the Arrêté of 29 Thermidor an VIII (17 August 1800), in which it was no longer listed as a rank, regardless of the fact that, of course, the function continued to exist.
Instead, two classes of Capitaines de vaisseau were introduced, but the 1st class was actually divided into two. The former Chefs de division were still highlighted as such in the États généraux de la Marine, despite belonging now to the 1st class of captains, and they were given priority over all captains of the 1st and, of course, the 2nd class (Arrêté of 7 Fructidor an VIII = 25 August 1800). This subdivision into - actually - three classes of captains remained in force throughout the entire duration of the Empire. All États of this period distinguish:
a) Capitaines de vaisseau de première classe qui étaient Chefs de division
b) Capitaines de vaisseau de première classe, qui n'ont point été Chefs de division
c) Capitaines de vaisseau de deuxième classe
Captains who were once Chefs de division are likely to have kept the star on their epaulettes - or were allowed to keep it if they wished so. And, indeed, quite a number of portraits of Capitaines de vaisseau dating from the Premier Empire and early Restauration periods indicate that this rank insignia continued to be worn despite the abolition of the rank itself.