About the Blessing of Light and the Echo

[Carin-Eri]

Well, from what I recall, Elidibus (in Shadowbringers) made reference to the Echo being 'gifted' to those who witnessed a Calamity that bore resemblance to their innate ancient memories of the Final Days.
However, that creates a problem in itself in my opinion, since it does make one wonder why the Echo apparently didn't awaken in anyone who saw (but didn't succumb to) the blasphemies, the epitome of the Final Days.

Still - we could possibly assume that it could be triggered naturally under the right circumstances.