Question: In the scene where Tex is terrorizing Reggie by lighting matches very close to her face, why didn't she just blow them out? This scene has always been a pet peeve of mine in an otherwise fabulous movie.
Question: When the Inspector said "We discovered your husband's body lying next to the tracks," I assumed that meant no one actually saw Dyle toss Lampert off the train. And since Lampert was killed in his pajamas before daylight, I assumed that meant Dyle first confronted him in his compartment. So after the murder was committed but before it was discovered, why didn't Dyle retrieve the travel bag, or at least take the agenda, letter and key with him?
Answer: Dyle didn't know that what he was looking for was inside the travel bag. Lampert had used the stolen gold to buy the rare and valuable collector stamps. He then affixed them to the envelope to look like ordinary postage. Dyle, who was impersonating a government investigator, was also letting Reggie (Dyle's widow) figure things out about the key, letter, etc. As Lambert's widow, she had access to her late husbands property and, eventually, would have unwittingly led Dyle to what he sought.
raywest
Question: When Audrey Hepburn confronts Cary Grant by saying that Carson Dyle is dead, shouldn't he have asked her how she knew that fact? (00:50:57)
Answer: Grant is secretly investigating the case and already knows that Carson Dyle is not dead, and has probably figured out how Reggie (Hepburn) knew that fact or else it doesn't matter.
raywest 
Answer: Blowing out the matches would only incite Tex to act even more aggressively and threateningly. Reggie knows he is not intending to hurt her and only wants to frighten her so she will cooperate in finding the money. Even though she is scared, it's wiser to remain as passive as possible.
raywest