What considerations should I take into account when installing XenForo v1 to make it easily upgradeable to XenForo v2?
What is that of "utf8mb4"? The tables in XenForo are UTF-8?
Utf8mb4: The database system Mysql had a problem a while ago ... what they called utf8 was just the most used part of utf8, but not all of it. As result, many unusual characters, and these new emoji things too, couldn't be saved in text columns of a Mysql database.
That was fixed some time ago (version 5.5.3) - but not by fixing their utf8 (because changing it would break some existing things), but by introducing "utf8mb4" which is their name for full utf8.
Measning, if someone wants to use emojis and the other unusual characters with Xenforo 1, it's still not possible, because Xenforo 1 doesn't use utf8"mb4". Now, with XF2, you can.