Self-destructing messages are security theatre with no guarantee that it's actually happened, I believe that was Moxie's answer when that was last asked. From what I recall, anyway!

He's wrong, oddly. For many scenarios, Signal would be better off if it offered a timer. After all, it offers a count-based deletion system (delete messages when conversation > X msg).

The only issue is in pretending this removes the message from the other side (like Telegram). Bury it in advanced options, put up a big warning or whatever. But to say people will get too confused and think it magically deletes other people's data ... that's a poor deal for serious users.

As-is, Signal users must diligently wipe information in case they are, for instance, stopped by police. Or in any other situation where they might be deprived of access for a bit, then be compelled to open the device. Perhaps they were in the middle of talking to someone. With a 1-5 minute timer, Signal can be useful enough to chat, while not risking too much if it's forcefully removed from you.

It's also just good hygiene in general. Most people are probably better off having old data get wiped automatically some time later. Opt in to perma-save. It's not comprehensive, but it sure helps users avoid an accidental disclosure.

And no, length limits are not good enough since they span an arbitrary amount of data and time. In fact, I'm not even sure of the point, unless it's to speed up the UI or something.

The Compartmented Mode Workstations with all their security features weren't rated to stop skilled hackers. So, what where the restrictions for? Answer: to prevent users from inadvertantly screwing up their own security plus make casual attackers work for it a bit. Making stuff automatically disappear unless you mark it permanent automatically reduces the amount of stuff someone will get from snatching your phone. That's why it's a good idea.

Side effect: may reduce information overload or search time for important messages. Unproven. Just a guess.

Guaranteed self-destructive messages, readable by human senses (and therefore cameras and microphones), are not possible.

Wickr

On top of it not disproving the rule, it's a bad reply for a number of reasons:

https://maqp3d.wordpress.com/2015/10/03/wickr/

Yikes.