After running a poll on on the subject of single keystroke commands (SKCs)[0] and in light of reported issues such as Bug 777022 and especially Bug 733339, it seems that Geary should default to using only normal keyboard shortcuts for actions instead of single keystroke commands (SKCs): E.g. Ctrl+A instead of just "a" for archiving messages.

However according to the poll results many people do still prefer SKCs, especially those coming from GMail, but also people are reporting the current SKCs compared to GMail's are suboptimal (e.g. Bug 778616).

So, to address both sides of this, we should introduce an optional "GMail Mode" pref that defaults to being disabled. When disabled, all actions are activated like any other GNOME app - using Ctrl and some other key. When enabled, these still work, but the user can then also use a set of SKCs that more closely match GMail's SKCs.

This will require Bug 778738 being implemented to work properly, and likely involve adding a bunch of additional action signals.

[0] - https://mail.gnome.org/archives/geary-list/2016-September/msg00073.html