Yes. If you simply delete the post, it affects the message count and the >>reply system. Consider a reply that says >>3,6-8,11. When 7 is deleted, manually updating that >>reply string to >>3,6-7,10 is just a lot of work.
>>2-4
Obviously, you have never programmed a textboard before.
>>5
Kareha is public domain software. Why don't you program a report system if you're so clever? It shouldn't be that hard; client-side JS or no.