[coldbox:6338] Rendering a Handler's response into a contentvariable?

I think you are.

From the point that you can separate the logic in the viewlet, this means that you can call rumEvent to return the data in the view itself and still be able to keep the view and logic separate.

But suppose you want *all* non-admin pages to be commentable? You'd
put the comment rendering into your layout, but who gets the data?
Only option I see is to do it as a viewlet, pretty much a controller
call that gets its own data and and renders it mid-request. That sort
of turns the layout into a controller, as opposed to a
pre-layout-rendering hook that could just get data the layout plans to