- Make sure you test clearing this data in a non-production environment first.
- Always make backups before you lose data forever.
- Make sure you're
truncate
ing, notdrop
ing. - Probably a good idea to reindex everything via shell after mass deleting records
To expand on Jim's answer, Magento Support doesn't need the contents of these tables when they ask for a copy of your DB, so you could consider them non-essential.