Not sure.
Are the <div> tags still in the content after saving it?
And in what kind of content are you placing this? In an article? In some field? ...?
It is working fine on my test sites. So guess it has something to do with something on yours...
Can you give me (super) admin and (s)ftp access so I can take a look?
And tell me on what url I can see/reproduce the issue.
You can use the 'Confidential information' button in the forum editor to hide sensitive information.