quark,
Since you agree that it is assur, you should acknowledge that there is no halachic basis to be lenient about texting, and it is purly rationalization to defend texting on Shabbos.
Again I will say that it s addictive behavior, which needs a level of yiras shomayim to overcome which sadly and tragically many of our teens do not possess.
This is yet another compelling reason why teens should not have texting available on their cell phones (FTR, IMO most shouldn’t have cell phones at all).