So I once again got a high CPU warning on the site. I go and check the logs, and I find that just querying comments is slow. This is what they told me last week, and I optimized the tables then; I didn’t espect to have problems again so soon.
A quick Google led me to the Codex where I learned that all those comments I marked as spam (many of which are marked automatically) are all still stored.
This quickie step took care of fully 14MB worth of spam comments out of the 25MB comments DB:
DELETE FROM `wp_comments` WHERE `comment_approved` = ‘spam’
I guess this means that the blog can run another year before I need to upgrade hosting!