Take y-axis scrollbar's offset into account for calculating popdown coordinates.

In current version popdown coordinates are defined by position of cursor when it's clicked. It works well until user scrolls a page.

Try this:

When page is loaded scroll down to the end of post and click on the word that you want to report. Popdown will render at the very bottom of the and may not be seen at all (zoom out on the document).

The same issue exists for horizontal scrolling if block containing text has fixed width.