What is the chidush in saying that it is ussur for him to talk in shul? Thank you for answering.
Aharon, London
Dear Aharon,
The Schottenstein edition of Artscroll (note 11) quotes Talmid Rabeinu Yechiel m'Paris that Yoshev b'Mekomo means in shul and all places of gathering. The Isur then includes all places of gathering.
The Rambam (Aveilus 7:5) writes "he should not leave his house to another place the entire first week ... the third he sits in his place and doesn't talk as usual."
See Gesher ha'Chaim Vol. 1 p. 226 in the note that he is not to speak as normal in public.
Idle chatter is forbidden in shul. Perhaps here the Gemara is telling the Avel to cut down even on permitted talk such as greeting or blessing others and Divrei Torah since he is in a public area.
All the best,
Reuven Weiner