After some experimentation I discovered a somewhat simpler method for eliminating the border around images in the 'Inuit Types' theme, and I offer it here for those who may not be inclined to muck about with HTML.
1. Open your Post or Page for editing; In the 'Visual' side of the Dashboard Editor place your cursor in the location where you would like the image to appear, then click on 'Add an Image', the first icon in the 'Upload/Insert' features.
2. Select an image from your Media Library and click 'Show'.
3. Select the appropriate size and alignment and click the 'Insert into Post' button.
4. The selected image now appears in the Editor. Click on the image; two icons will appear: 'Edit Image' (left) and 'Delete Image' (right). Select 'Edit Image'.
5. Click on the 'Advanced Settings' tab. In 'Advanced Image Settings', look at 'CSS Class'; a specification appears there (e.g., 'alignright size-medium wp-image-178'), delete everything except the alignment specification (i.e., 'alignright').
6. Below that, in 'Styles', enter (exactly as shown here): border: none; background: transparent;
7. Click update.
8. Now you can Preview or Update as usual to see results. Note that this will not work with images that you have added captions to. If you want borderless images with captions, you must add them to the image before uploading it into your Media Library.