I've just tracked this one down. logrotate is being run indirectly by /etc/cron.weekly/sysklogd, which contains the line:
for LOG in `syslogd-listfiles --weekly` I keep tracks of my local changes in a file in /usr/local/logs/changes.log, which is written to my a script of mine, which in turn writes to changes.log using local5.info in /etc/syslog.conf. I couldn't figure out why it kept being compressed and rotated, until I dug into /etc/cron.weekly and found out what is going on. Is there an easy way to stop this happening? If I hack /etc/cron.weekly/sysklogd, then it is going to get overwritten the next time sysklogd is updated. I can't see any 'exclude' options in the logrotate man page. Dougie