[jethro_tell]

They re-keyed it specifically so it could be nested, however, they mention the prefix key is intentionally dumb and ment to be remapped, probably to ^a like screen.

[entropie]

^a is the worst for emacs users since ^a is begging-of-line which we use a ton.

When I first started using screen some years ago the emacswiki (I think) even mentioned it and recommended to remap it to ^p which it is for me for screen and tmux since then.

(I could remember something wrong here)

[jethro_tell]

I mapped to alt space, which breaks things some times ten years on, but I just drop whatever is bound to that key in my DE and move on.

[DrillShopper]

I've just worked '^a a' into my terminal emacs muscle memory.