Not just the asterix, if you look at the first thing i posted it just says
(01:07:10) Chelle!supramad01@Chatter-A92EB388.too.secksy.France
That does not specify what channel has been joined. The second part I posted includes an asterix and 'has joined #Chat'
Edit:
This is a clearer example:
(01:50:46) * Snoopy (Bertrum@989981.d5c616.948a24.d4be1c) has joined #Paradox
(01:50:46) * Paradox sets mode: +v Snoopy
(01:50:58) * +Snoopy (Bertrum@989981.d5c616.948a24.d4be1c) Quit (Changing hosts)
(01:50:58) * Snoopy!Bertrum@blahblah.blah.France
(01:50:58) * irc.ParadoxIRC.net sets mode: +v Snoopy
(01:51:08) * +Snoopy (Bertrum@blahblah.blah.fr) Quit (Changing hosts)
(01:51:08) * Snoopy!Bertrum@blahblah.blah.Italy
(01:51:08) * irc.ParadoxIRC.net sets mode: +v Snoopy
(01:51:10) * +Snoopy (Bertrum@blahblah.blah.it) Quit (Changing hosts)
(01:51:10) * Snoopy!Bertrum@blahblah.blah.Ireland
(01:51:10) * irc.ParadoxIRC.net sets mode: +v Snoopy
(01:51:13) * +Snoopy (Bertrum@blahblah.blah.ie) Quit (Changing hosts)
(01:51:13) * Snoopy!Bertrum@blahblah.blah.Colombia
(01:51:13) * irc.ParadoxIRC.net sets mode: +v Snoopy
Notice how it doesn't show "has joined #Paradox" when it replaces the country code, only the first join which isn't a country code shows "has joined #Paradox"