Inspired by this tweet, I’ve decided to give WP-Sweep a try:
https://twitter.com/chemik3r/status/572127624346148864
WP-Sweep is a new WordPress plugin which only uses the official WordPress API to delete and clean up orphaned and unused data.
I’ve given it a try on my personal blog and it worked flawlessly. Unfortunately I’ve forgot to write down the exact percentages on what could be sweeped and saved but I have now a good feeling that at least my > 3000 blocked spam comments are finally gone 🙂
Don’t forget to backup your data, before you try this!