I'm not familiar with Julia, but I think a useful distinction can be made between input methods and ligatures. An input method is what you have to type to get a particular "code point" or character. Japanese, for example, is often typed using a latin keyboard, and as latin characters are typed, the application substitutes the appropriate Japanese character code point. For example, if I type the characters "n" (U+006E) and "i" (U+0069) using a Japanese input method, a に (U+306B HIRAGANA LETTER NI) (or 二 U+4E8C CJK UNIFIED IDEOGRAPH-4E8C or ニ U+30CB KATAKANA LETTER NI, or others as the case may be) can be selected to be entered. The actual character bytes will be substituted. You typed "n" and "i" but what gets stored is U+306B.

This is in contrast to ligatures: say if there's a fi ligature, I type "<" "=", and the "≤" character is substituted during rendering, but the individual characters are still the "character string". (You could also choose to directly insert the "≤" character directly, and that would then be a single code point, but I think for the purposes of this discussion, people are mostly talking about cases such as when the character string "<=" is rendered as "≤".

If Julia (like APL) uses characters outside the ASCII range as syntax, I suspect that there are input methods to assist in entering them as opposed to ligatures representing them on screen. But that's just naïve supposition on my part.

Another interesting case is TLA+ [1], where the language shares some LaTeX operators which can be rendered for display.

[1]: https://lamport.azurewebsites.net/tla/tla.html