Additionally, I discovered why '0' is being stored, because I use it as a reserve character for channels that don't have keys, when I'm joining many channels.
Example:
/JOIN #chan1,#chan2,#chan3,#chan4 0,0,key3,0
...where #chan3 has the key 'key3'
I can only assume /JOIN 0 (ie, partall) will record '0' aswell.
- Raccoon
