The Mishna on interrupting the Shema is on 13a3 (Artscroll English) in Berachos.
The TK states: in between the paragraphs, he may inquire for the sake of honor and he may return the person's greetings. Note 6 says this refers to an esteemed individual (Rashi) and one's father, teacher or anyone greater than him in wisdom (Rav) and a wealthy person (Mishnah Berurah 66:3).
Thus, between the paragraphs it seems as if there are a lot of people for whom you can interrupt.
The TK continues: In the middle of a paragraph, he may inquire only on account of fear, and he may return that person's greeting. Note 8: Rashi says this applies only to one who might kill him. Rosh and Rashba include a parent, whom one is obligated to fear (be in awe of).
Thus, do we today not interrupt for any of these? To make the question easier, let's say any of these parties (excluding the one who could kill you) were around at the shul.
I assume the answer is no. If so, why do we no longer act as the Mishnah states?
Barry Epstein, Dallas, USA
You are an observant Jew!
The Mishnah Berurah (66:2) writes "The Sefer Hachinuch writes that someone who we have never seen to be stringent regarding his friend at all, he (person Davening) should not interrupt even in between the paragraphs...According to our custom today, that we do not ask regarding people's welfare in shul, Chalilah to ask or to answer even words of Torah neither between the paragraphs (of Shema and its Berachos) and nor in Pesukei d'Zimrah."
All the best,
Yaakov Montrose