[tritosomal]

  That doesn't only mean "don't sext"

There is always a systems administrator in the loop WRT to your text messages, somewhere out there, in a server room, in an office park, housing data centers for service providers.

SMS messages cannot be assessed as "not posted online" anymore, due to the nature of the software used by service providers in support of SMS services.

If you send an SMS text message, by default you are likely posting it to an online system, even if your device provides no obvious indication of that fact.