If you're at CIA, messaging a colleague at all is absolutely work use.

Sorry but it's clear that in addition to — again — skirting the substance of the conversation, your barometer for just how security-conscious these types of organizations are is completely out of whack.

I think somebody is avoiding responding to the point, but I don’t think it’s me. Your comment was written in response to somebody saying that Signal is mandatorily installed on desktops in the CIA, making the point that it is probably used for more purposes than ordering coffee.

If you think the CIA’s own SOE goes against the CIA’s own guidelines, then yes there is indeed somebody tremendously, fabulously, loudly ignorant about how securities conscious these organisations are. That’s not me either.

If you cannot comprehend the idea that work computers or phones can have software that is approved for one purpose, but not for others, then this discussion can't go anywhere.

If you work at a healthcare organization, you may have Slack, but that doesn't necessarily mean you can message people's PHI.

At a financial institution, you may have email, but that doesn't necessarily mean you can email PII.

At CIA, you may have Signal, but that doesn't mean you can discuss ongoing military operations in it.

I have already linked to policy that explicitly says non-public DoD information is not approved for Signal.

I find it literally not believable that you don't understand this concept, so I'll have to chalk this one up to motivated reasoning damaging your ability to interpret English.