That's what it is.

They are all over the Internet and so is billet d'humeur...

just a suggestion.

The closest I can come, in English, to what this particular kind of writing is, is a *squib*--a very short newspaper piece used as filler. I realize that the "billet d'humeur" isn't really filler, but I don't think English has anything closer.

Here are a couple of instances where "squib" is used in the sense of short opinion piece:

Letters to the editor
... As for the other opinion piece, the author does not write with the approbation of the ... But reading the squib on Nov. 15 opinion page enabled me to resolve the ...
web.centredaily.com/content/centredaily/2000/11/22/opinion/ letters.htm

Assign#5
... opinion piece," or empty exercise in sarcasm: in other words, if we find ourselves sounding even remotely like a talking head on MSNBC, a "Vox Populi" squib in ...
www.nt.armstrong.edu/assign5.htm

Here is what Termium has:

ENGLISH FRENCH SPANISH
Subject Field(s)  – News and Journalism  – The Press (News and Journalism)
Subject Field(s)  – Information et journalisme  – Presse écrite 
filler Source CORRECT
media filler Source CORRECT
plug Source CORRECT
squib Source CORRECT, REGIONAL, USA
general feature Source
punk Source REGIONAL, USA
bouche-trou Source CORRECT, NOUN, MASC
article bouche-trou Source CORRECT, MASC
texte bouche-trou SourceCORRECT, MASC
article expéditif Source TRANSL. SOURCE, MASC
article de remplissage Source TRANSL. SOURCE, MASC
bouchage Source MASC
DEF – A brief, comparatively unimportant news item, sometimes used merely as a filler. Source
DEF – for "filler" : Short matter kept ready to fill space in a journal or magazine. Source
OBS – Can be used for public relations releases. Source
DEF – Petit texte rédigé au dernier moment pour remplir un espace resté libre dans la page. Par
extension, tout article de peu d'importance. Source
OBS – S'il s'agit d'une annonce, on peut préciser "annonce bouche-trou" (DUVIP, 1990, p. 224). Source
1992-02-03
 © Minister of Public Works and Government Services Canada

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Interestingly, the other meaning of "squib" is "a small explosive device," so maybe the equivalency with "billet d'humeur" isn't too far-fetched. After all, opinions are mostly explosive hot air, aren't they? ;-)

Here is one of the 8 entries in Termium explaining that meaning of the word:

ENGLISH FRENCH SPANISH
Subject Field(s)  – Weapon Systems  – Explosives and Pyrotechnic Chemicals
Subject Field(s)  – Systèmes d'armes  – Explosifs et artifices (Chimie) 
squib Source CORRECT
inflammateur Source CORRECT, MASC, OFFICIALLY APPROVED
DEF – A small explosive device, similar in appearance to a detonator, but loaded with a pyrotechnic, so that its output is primarily heat (flash). It is usually electrically initiated and initiates the action of pyrotechnic devices and rocket propellants. Source
DEF – Petit dispositif explosif ressemblant à un détonateur, mais chargé d'une substance pyrotechnique, de sorte qu'il produit surtout de la chaleur (éclair). Il est habituellement mis à feu
électriquement et il permet d'amorcer l'action de pièces pyrotechniques et de poudres propulsives pour fusées. Source
OBS – inflammateur : terme et définition uniformisés par le Groupe de travail de terminologie des Munitions. Source
1998-07-08
 © Minister of Public Works and Government Services Canada

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Evidently, there is a biography out there on Farley Mowat, the Canadian author, "WRITING THE SQUIB." If you've ever read any Mowat, that should tell you a lot about what squibs are! Here is what a reviewer said about Mowat, in reviewing that book. Note especially the last sentence!

"Mowat's writing is "subjective non-fiction" and he distinguishes between "fact" and "truth." The general purpose of his work is to educate and reform but his sense of humour adds a great deal of entertainment. Through his controversial works he has examined the concerns of the Arctic and its native inhabitants, Newfoundland, Siberia, the Vikings, the trauma of World War II, whales and other environmental concerns. Orange sums up Mowat as "anti-authoritarian, intensely nationalistic, environmentally aware, and passionately romantic." The title derives from a "squib," which is the fuse used to ignite explosives or witty writing; both meanings are appropriate. http://www.umanitoba.ca/cm/cmarchive/vol22no4/squib.html

Whimsy, whimsical or witty.

HTH