99% Invisible (a personal favorite podcast) just did a typically great short history of the interrobang and its fight for survival:
Today, the interrobang is just barely hanging in there. It has its own character in Unicode, the common directory of symbols which all computer fonts must reference. But Keith Houston points out that it still hasn’t cleared the biggest typographical obstacle of all: “I think that in order to really consider it to be a real mark of punctuation, people have to use it without thinking about it.” In other words: a truly remarkable mark of punctuation must be unremarkable.
I strongly believe in the interrobang. For my part, I created an iOS text replacement shortcut that replaces ?! with ‽ in my texts. This doesn’t pass the ease of use test, and it’s not available in every typeface. But it’s what I can do to help make the interrobang ubiquitous enough to save.
See also: Shady Characters