Basically it is just an informative message to remind administrators of telling your agents about the modification. Of course, there are some requirements for this feature to be displayed:
- You must be an allowed to manage the default translation (english)
- You must be an administrator
- The alias you are editing must be from the english folder

Here is how it looks like on the edition page:

How to enable this feature ?

By default the feature is enabled for all your translation tools. In case that you want to enable/disable the option, go to Dashboard > Modules > Languages:

Hope you will love this new feature !