I don't think that Herge intended any homosexual interpretation.
Perhaps not, I am frankly not sure. Note that in my comment I stated specifically that what Herge intended was besides the point in reading interpretations of the text. Figuring what he intended is very difficult, one has to ask at what level also, as we humans are very complex with our intentions. I think the text can always be analyzed as its own entity, and any consistent reading is a valid one, this is an usual approach in literary criticism. But again not the only approach, just a possible one.
I did not say that the gay interpretation is exclusive, that is, it is certainly possible to have a consistent reading of the Tintin albums where none of the characters are gay. I am just stating that it is a valid and consistent one.
You make very good points. I do think however that there is a bit of a difference between the Tintin series and some of other Belgian comics you cited. Especially given the nature of the evolution of the interaction between the characters. In the Tintin dialogue a stronger bond between some of the characters seems to be inferred, and there is a lot of circumstantial evidence that would support (though not completely prove of course) a platonic gay relationship.
The beauty of some of the best works of art is that they leave things unsaid and encourage the reader to make their own version of the story. There is a very famous short story by the Argentine writer Jorge Luis Borges called "Pierre Mennard, Author of The Quixote". In this story the main character; Pierre Mennard is stated to have re-writen an exact copy, word for word, of the Cervantes masterpiece, and in the act of doing it, to have written his own novel. In a brilliant piece of story telling Borges allows Mennard to create crazy and completely different interpretations of "The Quixote" in his exact re-writing, putting forth the absolute importance of the act of reading in the "creation" of a literary work.