SOLUTION

Either:

One cannot help feeling sorry for Montcorbier because his colleagues would seem to be treating him unkindly and judging him unfairly without any good reason for doing so. After all he has done nothing wrong. It is obvious he has some sort of problem as his strange behaviour and his losing weight would seem to suggest- "Moncorbier avait maigrii que sa tenue laissait supposer quelques désordres intérieurs".

It is true also that Madame Vesson was spying on him more or less. We read of the great delight she got from seeing him in the company of the "clocharde".

Or:

Montcorbier has done nothing to help himself vis-a-vis his colleagues: "Imperméable aux sous-entendus, il trainait une indifférence discrète…"

He ought perhaps to have communicated his problems to someone and in that way put an end to the rumours and gossip in the office. His behaviour makes people uncomfortable. He even makes it difficult for the boss to help him and was even insulting.