On Page 1, panel 1 of the color Tintin in the Congo, one of the reporters seeing Tintin off is a rather shaggy haired man with glasses, a black bow-tie and a brown suit. The same man appears again on page 2, panel 14 of The Secret of the Unicorn. The resemblance is quite striking. Is this man one of Herge's acquaintances, or is this just a subtle thing that Herge did just to see if anyone would notice?

It is Jacques Van Melkebeke, a friend of Herge, who helped him developing story lines for Tintin. Unfortunately, his relationship with Herge didn't end well.
You can also find Van Melkebeke on page 59, panel 6 of King Ottokar's Sceptre. In the same panel, Edgar P. Jacobs, Herge himself and Germaine (his first wife) can be found too.

Bachibouzouk

Thanks for your help. What happened to Herge's and Melkebeke's friendship?

According to Benoît Peeters' biography of Herge, a clairvoyant named Bertje Jagueneau was the origin of a quarell between the two men.

She told Herge that Van Melkebeke had some kind of bad influence or bad luck to him. And Herge believed her. There's also the belief that Jagueneau said that about a painting reprensenting Herge made by Van Melkebeke and given to his friend. They never saw each other again after 1952.

Here's a quote from Van Melkebeke, twenty years later : " Yes, superstition is anchored in the heart of men ! [...] I for my part knew a supposed clever man who did not hesitate to finish a relationship with an old friend on advice of a clairvoyant who had discerned a baleful aura to him."

Bachibouzouk

I didn't know that Herge was superstitious. Is this Herge biography in English?

I don't think so. Maybe it'll be translated soon, if the movies are successful enough.

It's called Hergé, fils de Tintin (Hergé, son of Tintin), and has been published in october 2002.

I learned a lot of things about Hergé in this book.