No, there doesn't appear to be a way to add a border outside of editing the code.
Add this to the other editor issues that haven't been addressed:
It has been very frustrating helping end users deal with Atto limitations.
Atto is a relatively new development, designed to overcome some of the shortcomings of both TextArea and TinyMCE, but in some ways it is so far behind TinyMCE still that it is proving somewhat less than useful. You should be able to change the default editor to TinyMCE in the Site Admin > Plugins > Text Editors > Manage Editors and swap the Atto for the the TinyMCE. That should solve your immediate problems.
Ryan is quite right though, while Atto shows some real promise, there does not appear to have been a lot of thought gone into improving the core Atto code, neither has there been a discernible amount of effort to do so. This seems to be coming back to innovation v polishing again.
Thanks for the tracker links and the info about the new editor/switching back to TinyMCE. It was a big concern of ours switching to 2.8 with (what I now know) the Atto editor was all of the anticipated questions on the new editor, why they can't go full screen anymore, why there's no option to add borders, etc.