According to the Digital Media Law Project:
"Publishing the Contents of Private Letters and E-Mail (including letters from lawyers threatening legal action): Fair use may protect the publication of the content of private letters and email, including communications from lawyers threatening legal action. As mentioned above, unpublished materials sometimes enjoy greater protection than published documents. Although an author may argue that the "unpublished" nature of his or her correspondence warrants a finding against fair use, such an argument carries weight only when the use involves a heretofore secret work “on its way” to publication, which is never the case for lawyers' cease-and-desist letters. Recently, two students at Swarthmore college posted an archive of internal emails among Diebold employees; an online newspaper linked to the archive in an article critical of Diebold’s voting machines. A court held that although the emails were not published, publishing them was nonetheless protected by fair use. Diebold, 337 F. Supp. 2

at 1203. The court found that the important fourth fair use factor weighed in favor of fair use because Diebold had no intention of selling the archive for profit and therefore it lost no value when the archive was published online. "
A few considerations: first, the value of the communications in question. Assuming we can equate "email" with "private message in a Diplomacy game," there is no value in the communication nor are any of us (nor Kestas, for that matter) attempting to profit from said private messages. Second, educational fair use is generally far more lenient than industry fair use. Students and teachers can do a lot more with copyrighted works than can an individual looking to profit from those works.
Also, we should remember that this site is the private property of Kestas. Since we are users of this site, technically his guests, and we did not sign a TOS, anything we say on this site is really the property of the site's owner.
Source: http://www.dmlp.org/legal-guide/fair-use