The problem affects our pluginuses jQuery's Sortable/Draggable feaure. When dragging a page (see attachment) the box is shifted.

The cause is that overflow-x property is set to hidden in the body. That property is set in the editor css.

So here's the deal.
Because of Quick Comments's feature the editor resources get loaded (asynchronously) when viewing page.

The problem is with a css setting in page-editor.css (top of the file):

body {
    overflow-x: hidden;
}

That that setting should be qualified to apply only for body.contenteditor. If you look at page-ditor.css everything is properly qualified (through classes and/or hierarcy).

So, it should be this instead:

body.contenteditor {
    overflow-x: hidden;
}