Hi,
So when a user is deleted you want all his/her threads deleted ? Are you sure ?
Removing replies (that do not have nested replies) could eventually be done, but how about topics created by this person that a lot of others have replied to ?
Is it not better to assign all the topics and replies to a used called e.g. ‘deleted_user’ ?
If you are interested in this proposal, let me know and I can see further what can be done.
Pascal.