Looking forward? That happened a year ago and caused problems because the OS X Yosemite login screen had no way to input emoji:
http://apple.stackexchange.com/questions/202143/i-included-e...
You mean é ? :-)
Also the default configuration for a couple versions now (which I hate, but I know it benefits others) is if you hold a commonly (western) accented character, it'll suggest accents for it.
option-u and then a vowel will create {ä ë ï ö ü ÿ}
option-n and then an 'n' will create ñ
Found this out while learning Spanish since holding down keys to select their alternate was way too slow.
option-n and then 'a' will create ã
option-n and then 'o' will create õ
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[1] Yes, I know you are OSX, but someone else reading this might not be.
By pipe, you mean "|", right?
That could be confusing to someone who doesn't know better.
A friend's project decided to disallow umlauts, combined characters like ´e (can't type the correct e with accent mark), the pipe symbol and a couple more in new passwords.
Not due to plaintext storage or so, but because of customer service issues - people were bugging support all the time because they were e.g. abroad and couldn't enter umlauts or on a Mac and couldn't find the pipe symbol (it isn't written on the keyboard!)... of course, a quick direction to the Zeichentabelle in Windows helped, but what for Mac users? At least it did take a huge load off the customer service guys.
I'm looking forward to the date when some clueless user will input a UTF8 emoji as a password, given that Android and iOS keyboards now include these on special keyboards...