Question: Are there any subjects that should not be discussed in a house of mourning?

Answer: Actually, halakha forbids a person who visits a house of mourning from starting up any conversation at all; he/she must wait for one of the mourners to speak first. Many times I have visited a house of mourning and have sat without saying a word, because the mourners did not speak. If I feel, as a Rabbi, that there is some halakhic or personal issue that I must mention, then I do so, but in general it is important, when performing the mitzvah of 'nihum avelim', to let the mourners set the tone.