Enabling the advisory mode by default seems like a mistake, at least with the current UI. It is so unobtrusive that it carries a very distinct implication of <i>"we've looked into this for you, and you don't need to worry about it"</i>, which is not the case. The iconography of the shield also implies this - it says "Signal is protecting you".<p>The message probably needs to be more explicit: <i>"Voltairine de Cleyre isn't using the same safety numbers anymore. Probably this contact just has a new phone or reinstalled Signal, but you might want to confirm the new safety numbers with them."</i>. And the accompanying icon should be an ! or ? or something.