Any SMS conversations that aren't with trusted friends. Like landlords, or bosses, or maybe arranging the visitation with your ex.
As far as an audit trail is concerned, you'd need to have all the cell carriers update their SMS infrastructure to save the associated edit history along with the text of each message. That's definitely non-trivial.
I'm not saying it's a bad idea to have this feature, just that it's much more work than you realize, and the benefit is probably not there to justify the work. Slack has the luxury of controlling their entire platform. They don't rely on Ericsson or Qualcomm or Nokia to implement new features the way SMS would.
As far as an audit trail is concerned, you'd need to have all the cell carriers update their SMS infrastructure to save the associated edit history along with the text of each message. That's definitely non-trivial.
I'm not saying it's a bad idea to have this feature, just that it's much more work than you realize, and the benefit is probably not there to justify the work. Slack has the luxury of controlling their entire platform. They don't rely on Ericsson or Qualcomm or Nokia to implement new features the way SMS would.