The X user, Fuego 7, wrote in May: “Xavier Niel I hate you I propose a one-v-one in front of the Lidl on Rue Sainte in Marseille.”
The commenter said slow internet speed on Mr Niel’s Free service had hampered their performance in Call of Duty, a first-person shooter video game requiring fast connection for online battles.
On Thursday, Free customers in Paris and south-east France suffered major internet outages for much of the day. It followed a hack on the company’s servers that led to the data of nearly 20 million phone and internet customers being leaked.
Mr Niel was in Marseille for a conference on artificial intelligence when he posted the video, six months after the duel was first proposed.
Fuego 7 then responded to Mr Niel on X, declining the billionaire’s offer of a brawl.
In all capitals, the social media user wrote: “No sorry I was joking,” before adding: “I would have liked to but 34.2 temperature plus stomach ache plus headache sorry I give up.”
Lidl’s social media team also joined in with the exchange, posting: “Please come and get the gentleman who has been tweeting since this morning in front of the store on Rue Sainte in Marseille.”
Mr Niel is known as something of an eccentric figure in France. In September, he published a book titled “A hell of a desire to make a mess”, following his journey to becoming a millionaire at the age of 24, having grown up in a deprived Parisian suburb.
The French businessman went on to become a billionaire after Free introduced a singular set-top box, offering customers internet, telephone and television services in one product.