How to delete records from Comment List

I am unable to delete entries from Comment List, which have been created after deleting lots of records.
for every record i delete, erpenxt is increasing enties in various places, so i am unable to delete record without keeping any trace of it… like deleting record affects Version List, Route History, Deleted Documents, Comment List. So, if i delete 100 entries, erpnext creates 300 / 400 enties at various Lists.

See number of records created after deleting 100,000 records of route history. And these are not getting deleted.

Above all, this exercise increased by disk space usage by 2GB !!

for better database management i use this. hope this will also help you.