And I have looked into it - and it already checks when editing:
Please provide your steps to reproduce the issue, in clear bulleted order and indicating exactly what is being done, and show what limits you have enabled for the user group for which you are testing.
My own personal suspicion is that they are disabling Javascript in their browser, then editing, but as the application uses Javascript to achieve what it does then there isn't much I can do about do outside of getting more involved in inspecting the submitted content, which is not something I'm likely to do with this application at this time.