Keep in mind that it's not a best practice to create a new field with similar function. Do I understand well that you now have a field caller which is not used at all and have a new one (most likely) u_affected_user that has the similar function? From my point of view it is definitely better to reuse what is there and adjust the name or behavior (mandatory/read-only/). I've been with SNOW since Istanbul and do not recall any field called "affected user".

How did you mean that with the asterisk? It's there and red if the field is mandatory, it's there but gray if the mandatory field has a value. You can either set this up to have static behavior by configuring dictionary or dynamic behavior based on UI policy or UI script (usually change behavior based on a value of this field or another field)