Rav Yosef tackles the sticky question of whether a person who pronounces Hebrew with an Ashkenazic pronunciation can fulfill his obligation in kiddush or keriat HaTorah by listening to someone recite it with a Sephardic pronunciation, or vice versa. This issue was a major debate between the early chief Rabbis of Israel (Palestine), Rav Kook and Rav Uziel. Rav Kook felt that a person is not allowed to change his pronunciation, as doing so would constitute a violation of al titosh Torah imecha, while Rav Uziel felt that insofar as both approaches to pronunciation are acceptable, there would be no problem if a person changed his own approach.
Following in the footsteps of his Sephardic predecessor, Rav Yosef sees no ptoblem with a person hearing kiddush or havdala from someone who utilizes the opposite pronunciation, and he extends this ruling to include hearing keriat HaTorah from such an individual. He furthers his discussion to include the phenomenon (perhaps recognizable today in the cases of students who learn in Israeli yeshivot) of students whose parents use an Ashkenazic pronunciation, yet they pick up a Sephardic approach in school. He says that there is no problem involved, as even within Ashkenazic pronunciation there are vast differences (such as the difference between a chassidish and a more yekkish pronunciation).
Nevertheless, Rav Yosef notes that for parashat zachor and parashat parah a person should try to hear those sections read in their own pronunciation style, inasmuch as they are doraita obligations.