When you are editing a feed, the UI shows a grid with the fields and a button for changing standardizer/validator settings: see attached screenshot:
This button, however, shows the text "ADD", which is kind of confusing for the end user.
Say you want to remove or update a validator, then you have to click on "ADD" first, then make the change (deleting/updating a standardizer/validator) and save: this is very counter-intuitive. For the first time I asked myself: where do I click if I want to remove that existing validator??
In my opinion, it would be better to change the UI so that when you are editing a feed, the button text is something like "UPDATE", "EDIT" or "CHANGE" as this indicates its true purpose (that is not only "ADD").