In the case of Slack though these are "private" communications only in the same way that say, email to colleagues at work is "private". Lots of people certainly could snoop this, and more probably would be able to if they really wanted to. You would not be told about that, it'd just happen and everybody involved would convince themselves that it's fine. Is it fine though?

Signal's rationale is that if we actually secure this type of conversation, we can tell people not to accept insecure conversations because they're trading something you might want (actual privacy) for... not very much.

We've been here before on the Internet, at least twice now. When I was still (barely) a teenager Tatu Ylönen invented SSH and connecting to another machine was now secure instead of hopelessly insecure. And at almost the same time a bunch of people at Netscape invented SSL (which became TLS) and made the World Wide Web secure. It only took a few years for ordinary (relatively) people to _expect_ SSH not telnet and it took a bit longer for HTTPS but in both cases we got to a place where secure was the default and expected condition.

Please recall that earlier in the thread, the following was posted:

"[Signal is] really an engine for revealing people's true preferences for messaging, which, for many people, tend to be that they want all the ergonomics of Slack a lot more than they want cryptographically sound secure messaging."

This comparison to Slack makes no sense - Signal replaces texts and makes them end-to-end encrypted. It's a straight upgrade to texting (except, apparently, on iphone, where apple won't let the app send plain old texts and the "drop-in replacement" quality is neutered). It requires a phone number to use, and is linked to that phone number.

Signal is right to be what it is, and if Apple got out of the way, I would insist on replacing all texts with Signal. Replacing my Slacks with Signal or my Signal messages with Slack fails to type-check.

One (Signal) is a replacement for texts, and one isn't. "Overlap in features" wouldn't cover it, but rather how much you want it to be like texting.

Thomas Ptacek is a big Signal advocate, as am I, but he doesn't like to think of it as a drop-in replacement for texting, whereas I do (because that's what it is and where it shines). I move texting onto Signal whenever I can.

Why not Keybase over Slack?

Not saying Keybase is better; no dog in that fight, just curious if you had considered it.