If such post is reported, do the mods have the privilege to edit the content?
Depends on the moderator but here in Meta, i don't think edit anything. It's all up to OP
Sorry I already signed the message with it
You can still sign a new message but minus the email address. You will just used the email address to send the message to the accounts recovery team. If you don't send any message, nothing will be done to recover your account.