Chopra Ji | [#GoodLife]Don't you even know basics of group chats?
I don't know how hard it is for people to understand that deleting messages after having a huge conversation isn't beneficial for anyone. If a third person sees the thread, it looks like that person is just talking to himself, making the whole thread nonsensical and useless.
If the thread is so confidential that you had to delete all the messages at the end, why not just use PM? At least it won't make the chat look chaotic.