To delete rows in your
wp_comments you can use an SQL statement like so
DELETE FROM wp_comments where comment_date < '2016-01-01' and comment_type = 'order_notes'
This will delete all comments older than January 1st 2016. I do believe Woocommerce uses
order_notes as a
comment_type make sure by checking that column before running the statement.
Of course, you need to adapt the
FROM wp_comments to reflect the prefix you are using in your DB.
Also make a backup of your DB BEFORE running this statement, it will ERASE your data!
here's an alternative statement
DELETE FROM wp_comments where comment_date < DATE_ADD(now(),INTERVAL -365 DAY) and comment_type = 'order_notes'
It does the same job but the SQL statement will generate the today date and remove 365 days from it and delete everything older than 365 days. I find it easier to work with. You could run this statement every month and it will always remove entries older than 365 days from run time.