I have no knowledge of these particular posters or their ISPs but I caution readers not to assume that identical NNTP-Posting-Host addresses automatically mean the same user; some small ISPs assign RFC 1918 addresses to clients and have a small block of public IPs exposed to the 'Net. Also, a public access machine or a shared machine in a residence may conceivably be used by different posters. Combining the weight of circumstantial evidence such as posting IP address, user agent, bang path, etc. together with an analysis of lexical style may result in a more cogent argument for a poster's identity.
Michael