Security of your account is super important and there’s changes coming to the amount of characters that can be used for your Battle.Net account and when logging into Diablo 3. This is a really important notice which you need to read because you may find yourself unable to login to Diablo 3 if your password is changed to exceed 16 characters.
The statement from Blizzard reads as follows:
To increase account security, we’ll be updating Battle.net on April 15 to allow your account password length to exceed 16 characters, the previous limit. However, it is crucial to note that Diablo III does not support passwords that exceed 16 characters.
We are already planning ahead to resolve this issue as quickly as possible, and plan to have a patch out that addresses this on June 9.
If your password exceeds 16 characters following this update, you will be able to log into and play Diablo III through Battle.net, but will not be able to log into Diablo III in-game at the account login screen until June 9 .
Thank you for your patience as we work on a solution. We’ll see you in Sanctuary!
The bottom line is to make sure you don’t change it to more that 16 when the new system kicks in otherwise you could be locked out of playing until 9 June. I’m sure nobody wants to have to wait that long.