deleting posts in chat

I have sent out a few requests for info on this but no one has answered me back. I would like to know how a person can delete posts in chat. I want to know not because I want to delete anything I have posted . This is about someone making hurtful comments and then deleting them. I don't think this should be able to be done. If anyone can tell me how this is done I would appreciate it
 
idk how to do it but if someone is doing that i would report them to a mod ,
 
I already have reported it to 2 Administers and a moderator and the Mod team has been put on it.
Thanks for the response.
 
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