Stoopid idiots!

Why does adding extra letters to letters you don't typically emphasize add emphasis?! Yeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees! < - just says "yees". which you don't say.
Shitttttttttttttttttttt! < - "shit-t-t-t"? you kiddin' me?!

I mean, I'm guilty of it on occasion, but I try and pick the letter that would be emphasized when I say it out loud.