Can you respond to קדושה if you are not already done with your own ש''ע? I heard that you can if you are past a certain point after שים שלום/שלום רב. I just want to know if that's true and, if so, ...
Is it considered a hefsek to play with one's fingers or silverware or such while waiting for the challah to be passed around on shabbat, after the blessing made on it? Even though it isn't talking, it ...
For what prayer responses (e.g. amen, baruch Hu uvaruch Sh'mo, y'he Sh'me...) may one interrupt his own recital of birkas hamazon?