The problem with restricting own-diary editing by default is that it would require admin intervention even for trivial reformatting and typo correction.
AFAIU, at present that becomes a delete ... indeed, it may well be that that is what "delete" does (I certainly have not looked at the code to know what the delete button actually does in process terms) ... it would have to be re-programmed to become dummy text, because the system is not set up to cope with posts with zero content, even if they do have comments attached. Utsukushikereba sore de ii
