I recently had a new member go back and delete every message she had posted, which took every reply members wrote. It was a little shocking. I felt the threads were valuable, especially to all the new members. I contacted her privately, and she said she felt shame and feared her questions were too simple for the level of experience in the group, even though she had received many good replies. I asked her not to do that again, since her questions were undoubtedly wondered by others new to the industry, and also because many people had spent time providing helpful answers. People are not going to bother responding to questions if they are simply deleted.
Then I immediately changed the settings so that no members could edit or delete their own posts. Just too easy to do for some people!
I decided that if a group member really wants to make edits to their message, they can contact me privately and ask me, as Owner, to do it for them. They can send me what to copy/paste onto the message. I don't think it'll happen too often.
Jen