The 'tags' plugin of pyblosxom was kindly forgetting about sorting entries.
pyblosxom is the first real python code I've put my hands on. pyblosxom isn't too bad, but my impression after seeing its plugins is: "why do people choose python because of its elegance, then write really ugly code with it?"
At least the blog is currently fixed. If someone wants the patch, ask me and I'll be glad to send it: I gave up contributing them back to authors that haven't replied after months.
I'll try to survive with this until a new Debian Stable includes Rails and a Rails blog I can play with.