[kertoip_1]

> They impose minimal privacy risk.

Absolutely not. Privacy risk depends on how well protected is the weakest point in your network. So if one of the participants' device is compromised then the entire discussion is compromised too.

On closed, proprietary platform you just cut off the weakest point from access to the data when you suspect it is not protected enough, as data it lies on a single server. On mailing list you can't do anything, because data lies on somebody's else's server