There are differences between personal and communal sacrifices: one can make (forbidden) exchange with personal sacrifices but not with communal ones; personal offering can be males or females, but communal offerings are always males; personal offerings that need to be brought at specific times (for example, of a Nazir) must be brought even if its time has passed, but communal offering need not be brought after their time has passed. On the other hand, communal offerings can be brought on Shabbat, and even in the state of impurity, but personal offerings cannot.
Rav Dimi had a clarification for these rules, concerning libations. He said, "If I had someone to carry a letter go Babylon, I would write and send this clarification to them." But would he send it? The Torah said that “Write these words...” refers to the written Torah scroll, but “Through these words” refers to all other laws that one is not permitted to write down! – A new law is different, for it is better to violate the Torah prohibition of writing than risk whole Torah being forgotten.
But how can the Talmud even ask such a question, when we know that Rabbi Yehudah the Prince collected and published the Mishnah, and Rav Ashi collected and published the Talmud? – There are two versions Rav Sherirah Gaon's letter, and according to one, they only collected but did not publish.
Art: Gabriel Metsu - Man Writing a Letter