In the film 'Gravity', astronauts can be seen having casual chat with mission control. Do astronauts do that in real life? Do they have any specific policy that states what can be communicated over radio?
If you listen to live (or recorded) ISS to ground conversations you will find that the astronauts are human, and have perfectly normal conversations when not specifically running through mission checklists etc.
These conversations include banter, birthday wishes, conversations about the weather (yep - seriously) and any manner of normal topics.
I couldn't find any examples of swearing or offensive language, so there is probably a directive to avoid cursing on air (that is just a guess of mine though)