Interesting how the domain is shown here with an extra period at the beginning "Hey Rails, nice Rack! (.brainspl.at)". I am guessing it must be coz it is a bare domain (no www) and pg is working his way backwards from the first single / (or eol) and he expects at least three parts: TLD, domain name and subdomain name and puts "." between each.
Actually, someone suggested I look at the source code rather than submit a ton of URLs and try to reverse-engineer the logic by looking at the results. Here's the relevant code fron news.arc:
(defmemo sitename (url)
(let toks (parse-site url)
(if (isa (saferead (car toks)) 'int)
(tostring (prall toks "" "."))
(let (t1 t2 t3 . rest) toks
(if (or (mem t1 multi-tld-countries)
(and t3 (mem t2 long-domains)))
(string t3 "." t2 "." t1)
(string t2 "." t1))))))
; Minor bug: can have both google.at and google.co.at. Same for jp.
Update: Did a quick test.
Submitted: http://127.0.0.1/this/that
Showed up as: (1.0.0.127) !
Wow that is totally not what I expected.