As a workaround, set LOCKFILE=/var/lock/acct in your /etc/defaults/acct. Editing /etc/init.d/acct directly is less desirable, as Debian maintainters feeling too righteous are known to delete init.d scripts they deemed "obsolete" without any warning, while config files in /etc/defaults are relatively safe.
(I got my /var stuffed with ever-growing /var/log/pacct as the rotation stopped because of that stupid "subsys" shit. If this is not a sabotage, then what it is?)
