Twitter has a search bar thing and in it, it says "enter a @name or username". Now, I've been pronouncing @name as "at name", because that to me is an "at sign". I don't know if twitter is calling it something else. That's what the article "a" rather than "an" suggests. But what could it be calling it?
In other languages, it's called things like "monkey tail", "elephant's trunk", "little dog", "snail" and other animal-based names reflecting its shape. But in English it's really only called the "at sign".
So twitter, why you no obey phonological rules?