If you select "Number of comments" is less than or equal to zero, it's the same as selecting "unlimited" and the entire forum will be wiped out. Zero should not even be a selectable option if it is the same as unlimited.  My goal was to kill threads with zero replies, but selecting 0 killed all threads and now I'm doing a DB restore.

 

Thank you for bringing this issue to our attention! I have logged this internally for review.

 

This has now been resolved in the 4.7.16 release. Please update if you are seeing this issue. If you are then still seeing the issue, please let us know.