[pfortuny]

“didn’t you read my message? I said at 19:00.”

You said “9:00”.

“go check”.

and that for a simple interaction, imagine a complex argument...

[aaron695]

If your friends are lying to you then that's not a message problem.

Plus it's silly, most mark the message as changed and some have an audit trail like Slack.

I'm not sure what scenario this plays out in?

[function_seven]

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.

[pfortuny]

Any meaningful conversation in which past words are important for the contents of the message.

I mean, do I really have to reread all the "marked as changed" messages even though only a tiny part may have changed etc...?

Normal people tend to fare very well with "sorry, made a mistake: ...."