I haven't had a problem with indicator visibility, but I remember spending some time getting it to a place that worked for me.

Here's what I use:

  set -g status-left "#{?client_prefix,#[bg=colour76]^,#[bg=colour235]_} [#S]"
  set -g status-right ' | #[fg=colour76]#h#[fg=default] %H%M%Z'

I don't mean rendering of an icon so much as I mean that humans become blind to persistent things (and frequent things). Losing glasses on your head kinda thing. I don't find a mirror as helpful as having a fixed location to put my glasses when I'm done with them. Same strategy

But yeah, when I didn't have splits and things in my emulator I used something like you did. Make a remote section visually distinct. To a lot of extent I still do, just this isn't necessary through tmux anymore