As we know, there are two main forms of Hebrew: Ashkenazi and Sefardi. And the most notable difference between them is the pronunciation of the last letter, the ת, as either an S or a T.
Though the T-sound is considered Sefardi, I hear plenty of Ashkenazim using it. And I hear people who constantly switch around between the two, using them interchangeably, sometimes even in the same verse! (Example “YiTgadal V’YiSkadash”)
How important is it to pronounce this letter according to one’s heritage? If one pronounces it differently from one’s family custom, is the prayer or blessing still valid? If a Torah reader pronounces it unlike his tradition, must he be corrected? How about if one suddenly decides to change because he joins a congregation that does it the other way or simply wants to?