You can edit your own work if you let it sit for awhile. But it is always better to have someone else look at it. The differentiation made here between line editing and copyediting doesn't really apply to newspapers — because most of the writing is on deadline. So the assigning editing does some line editing and the copyeditor may do more. What strikes me about much that I see online is that it goes on too long and has a tendency to digress too much.