Text-message shorthand conventions arose from the users, because the need to type quickly on a tiny keyboard was greater than the need to spell correctly and preserve the subtleties of punctuation. But as users find more ways to hash and remix their social networking, a new set of technical needs may give rise to new conventions.  Mike Arnzen alerted me to Microsyntax.org.

Many people don’t remember that the use of ‘@’ to indicate that a
message was to be sent to a specific user’s attention (a reply or a
mention) is a convention that grew up with the service’s earliest days.

We have some relatively mature conventions — like hashtags
(‘#twitter’ or ‘#ruby’, for example) — that have spread into wide use
but are not directly supported by Twitter itself, and where different
applications may support them in very different ways.

At the other extreme, we have new conventions appearing — like
CoTweet’s use of ‘^’ preceding initial of authors in group twitter
accounts, my recent suggestion for ‘/’ as syntax to precede or enclose
locations (as in ‘/Germany’ or ‘/156 South Park, San Francisco CA/’),
or my proposal for subtags (like ‘#sxsw.kathysierra’ or ‘#w2e.PR’) —
and these could lead to confusion or conflicts between contending
approaches to the same purpose. — Stowe Boyd