I agree, but my original comment was just presenting one of the things to concider before making such addition.
As I pointed out earlier, it might lead to more unnecessary chat abuse (or not; maybe I am just overthinking).
Another thing to concider is the fact that it is just a single target ultimate. So, what will this mean for other champs and their ultimate abilities?
I already see posts of people saying that X champ is "unbalanced" because he does not say Y when he does Z.
The bottom line is that it's an arena game first and RPG second.
Otherwise, I could argue that if this was added, then I want Nidalee to roar globally everytime she turned into cougar.
An ult that would provide such interaction should interact globally with all enemies/allies.
Take DOTA2 as an example. Silencer's ult silences all sounds when it's active. It's a global ult that affects all heroes. Zeus's ult does same and has lightning sound all over the map. Chen heals all allies and says something to his allies.
Garen's ult is not global, so why should it be special?