Hah, saw this post merely by accident.

That's an interesting kind of hint, though not as hard as you think (took me about half an hour)

To run the first time: /plot <string>
To get results: $plot

Example:

/plot this is a test

$plot -> **** ** * ****
$plot -> t*** ** * ****
$plot -> t*** i* * ****
$plot -> t*** i* a ****
$plot -> t*** i* a t***
$plot -> th** i* a t***
$plot -> th** is a t***
$plot -> th** is a te**
...

Code:
alias plot {
  if $isid {
    if %plot.pos == -1 { inc %plot.pos }
    elseif * isin %plot.cur {
      while !$regex(plot,%plot.cur,/(?=(?:\s|^)[^*]{ $+ %plot.pos $+ }(\*))/) { inc %plot.pos }
      bset -t &amp;raw 1 %plot.raw 
      bset -t &amp;cur 1 %plot.cur 
      bcopy &amp;cur $regml(plot,1).pos &amp;raw $regml(plot,1).pos 1
      set %plot.cur $bvar(&amp;cur,1-).text
    }
    return %plot.cur
  }
  $null($regsub($$1-,/\S/g,*,%plot.cur))
  set %plot.raw $1-
  set %plot.pos -1
}

Gone.