By "Isolated Name", we mean that a first name and last name were not both included when the person posted to Usenet. The person may have included initials instead of their first name or last name, for example. The person may also have entirely omitted their first name or last name. Another possibility is that the person posted using a nickname or pseudonym. Finally, it's possible that this isolated name is the person's full legal name, especially if the person is from a culture that does not have separate first and last names.
Here are some examples:
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