As a first time poster, however, I could not have tested my image upload embedding by editing an earlier post
I don't understand. You can do more when you edit a post than you can when first posting it.
One clear example is uploading images to Dave's server (ie. "Attachments"). You only get a thumbnail at the original post. You can then come back and view the thumbnail to get the full sized image, copy the image address and then update the post with the
[IMG] tag containing the image URL