Isn't that exactly why emoticons were "invented"? Even a well-placed "lol" (used to be just ":D") conveys a lot about your emotional state when writing that sentence.

They are absolutely critical (and still in use) in mediums like IRC to avoid misunderstandings. Less so in long-form, low-frequency communication like SN where you can craft your message more carefully.

I don't understand why, over time, the culture of the Internet evolved to shunning them and generally considering them "something only teenagers/facebookers do" (in a pejorative meaning).