Comment 6 for bug 1526717

> Can't reproduce this part: dragging a guide within the select tool
> context is not cancel-able (not with earlier and current stable
> releases either, so never was). The only thing that 'Esc' in that
> context does while dragging a guide is deselect any current regular
> selection.

You have to pick the guide on its origin with the select tool. If you pick the guide anywhere else it works as you described.
 - have a guide in the document;
 - draw a rectangle;
 - press F1 (select tool);
 - pick a guide on its origin and drag it;
 - while dragging, press ESC: the guide detaches from the cursor and the rectangle is deleted.
I just tried this in the document I'm working on.