I am still a fan of the "proper grammar" we learned in school. As to the issue of dropped punctuation and other grammar atrocities, thank SMS -- old school text messages. Then came Twitter, and in the beginning they had a SMS-to-Twitter function (or something like it). Last, shrinking devices and crappy typing experiences. T9 was amazing but inferior to a real keyboard. Today, all thumb-typing virtual keyboards are a…
Punctuation is a way of communicating tone, and a more friendly way of communicating is to omit periods. Note that omitting a question mark actually makes a message less friendly, so it’s a matter of observation and convention rather than inherent nature. For example, repeated commas,,, give more of a trailing off tone than ellipsis... which indicates a pause. I think kids get this kind of stuff intuitively and adults have to be told more often.