I completed and sent a form about a ghost Shell garage on 19th December. I understand there may be delays in fixing these, but I have had no feedback or acknowledgement at all. A short message back would be good as it is never certain that these online forms are actually sent successfully.
Update HQ have dealt with all of the ~35 reported stations so far, except for 3 they couldn't find (see link above). Specifically, they've removed any gas stations at those locations which did not have a matching Landmark in the editor.
If you find any more ghost stations, please submit them via the form.