There is a rumor on Twitter that Harry's character cries/sobs in one scene. The original rumor stated someone who saw Dunkirk said Alex cries over a dead body, and a variant of the rumor is that he cries reading a letter. I think the variant is definite bs because there are fans who believe there is a scene of Alex reading a letter on the train but I believe that photo during production is of Harry reading a piece of script on the train. One fan on twitter said "What if Harry cries while reading this letter?" and I think that is the source of the variant.

Since there I could find no English or French source of the crying over a body rumor, and I was was not about to search Twitter for Harry/Alex and the word for crying or sobbing in various languages and tenses, there is currently no findable basis for this rumor.

crying/sobbing over a dead body

someone important for Alex dies, and from what we've seen of the filming process now we wonder if that could be Gibson or Tommy.