If you have found an obsolete feature and deleted it, we would greatly appreciate it if you'd leave us a note in the comment field in the editing window briefly explaining why you deleted the point. We kindly request that in your comment you include links to the sources you used to confirm why the structure no longer exists. This information is really helpful to the USGS structures team.
Personal knowledge is also an acceptable reason for deleting a feature, just make sure to include a note about the work you did to confirm that the structure no longer exists.
If you are deleting a point, you do not need to hit the save button before deleting it. You can delete the point immediately after making a comment, and the comment will automatically be saved to the edit history for that point.
You can also use the comment field to cite any authoritative sources you used to verify a point, even if you aren't going to delete it.
If you are not deleting the point, then you will need to hit save after entering your comment or making any other changes to the point. The comment will disappear from the editing window after you've saved your point, but it will be visible in the edit history.