Comment 1 for bug 741462

The close-on-blur windows (popup) are the preferred design in lazr.js. The overlays that you must dismiss were added later. Since the content exceeds the size of the viewport, the must remain visible when the user uses the scroll bar. Both kinds of windows are used by Canonical sites, and both will remain until UX says otherwise.

I think the crux of the issue is that engineers are required to style the popup and overlay windows, and when given a choice, Lp engineers prefer to make their work exceptional. I recently reviewed a change that introduced a small overlay, it will never exceed the viewport, so the developer made it look like a popup, but did not behave like a popup.

There are two things we can do to address the issue. Firstly, make the designs of popups and overlays more distinct. Secondly, create widgets that enforce the designs; the engineer cannot easily make change the style.