Why don't I see the standard Case field 'Internal Comments" show in the SF Classic, the Salesforce1 mobile app, or Lightning Experience
|Knowledge Article Number||000232612|
|Description||Why don't I see the standard Case field 'Internal Comments" show in the SF Classic or the Salesforce1 mobile app or when using Lightning Experience when editing a Detail page or within an action :
|Resolution||The 'Internal Comments' standard field that is under the Case object, is a field which is currently NOT supported in SF Classic, the Salesforce1 mobile app, or Lightning Experience.
Reason being, the field is essentially just a short-cut to creating a Case comment. Please know, our R&D team is aware of this issue and have logged a feature request, with no ETA specified.
Take note, that this is NOT a BUG, as the field was not intended to be supported.
That said, as a workaround, you can always create a Visualforce page to achieve this functionality in your Org. Or in the case of Lightning Experience you would need to switch to the Classic UI (Aloha) to utilize this field.