Handling of special character is usually a bigger problem than unicode. Just today, I tried to name a file with both a single quote and an exclamation point from bash shell. Ended up doing that with a GUI file manager.
mv foo \!\' $ touch 'j-kidd'\''s file!'
$ ll 'j-kidd'\''s file!'
-rw-rw-r-- 1 uid gid 0 Apr 11 13:30 j-kidd's file!
$ ls "!$"
ls "'j-kidd'\''s file!'"
ls: cannot access 'j-kidd'\''s file!': No such file or directory
$ ls '!$'
ls: cannot access !$: No such file or directory
"directly adjacent strings which are double quoted, "'single quoted or even'\ unquoted\ and\ possibly\ full\ of\ escape\ sequences\ 'get concatenated and count as a single parameter.'
Running touch on the above will create one file with very long name.
Or, "don't be your computer's tool!" -- the operator should accept no arbitrary limitations.
That also lets you write confusing filenames like "foo\rbar". Which can be really irritating to figure out without a GUI.