While coding[isn't that where ppl realize they don't have what they need?] I realized there wasn't a decent way to test if the buffer of a window has changed, be it due to user's /echoing, an error in a script, etc

So I suggest one of two ways:
Code:
on *:BUFFERCHANGE:window:{ 
  $target == window whom's buffer has changed
}
and/or
Code:
/window -Z name
  Resets $window().CBuffer to $false

$Window().CBuffer
   returns $True/False if the buffer of the specified window has changed since the last /window -Z