PARIS — He and his writing partner were the toast of the Left Bank, published and celebrated by the prestigious and chic. They were praised as authentic voices from France’s troubled suburbs, articulate and poetic chroniclers of the immigrant youth experience.

Barely into their 20s, Mehdi Meklat and Badroudine Saïd Abdallah — “Mehdi” and “Badrou,” as they are known — were stars of Bondy Blog, a much-praised chronicle of suburban France sponsored by the mainstream press. They were seen poolside in Los Angeles and at Le Select in Paris, and had their own show on national radio, all the while going home to the cramped housing projects of their parents in the suburbs.

All that is gone now. Mr. Meklat, 24, is now a media phenomenon of a different sort. He has been revealed as the semi-hidden author, under a pseudonym, of hateful and obscene tweets — anti-Semitic, misogynistic, pro-jihadist and homophobic.

“Bring on Hitler to kill the Jews,” he tweeted during the Césars, the French Oscars ceremony; “Charb, what I’d really like to do is shove some Laguiole knives up his … ” he wrote about the Charlie Hebdo cartoonist, not long before the massacre in which Charb was killed; “I find the phrase, ‘I love death the way you love life,’ of Mohammed Merah troubling in its beauty,” he wrote about the murderer of Jewish schoolchildren in Toulouse; “I miss Bin Laden,” Mr. Meklat said in another tweet.