Yes, the trigger for my question was the statement of Theymos about that evtl. the account registration IP would have been stolen. And I was wondering, why that year old IP address would have to be kept in the database, while I think in the meantime I have proven not to be an attacker / spammer / bot, whatever bad.
It's possibly logged for any suspicious activity on your account. Although, it wouldn't be a major indicator, it would be a factor of multiple irregularities. Whatever the reason for it, only administrators can access this data. So only theymos, Badbear and Stefan Thomas has/had access to this information, bar the recent compromise.