If we think of this as two distinct layers, the detection layer and the presentation layer, it may be simpler for you to modify only the presentation layer, so your users don't see the unwanted asterisks, while leaving the detection layer unmodified, which stores the error with the asterisks.
Please try using the custom error section, available on the Display Options tab of the harness rule, to modify the presentation layer. Be sure to check the documentation for what is required in your custom error section, and make sure the section is included on your layout.
The only way to remove asterisk is to customise the error section I believe. There is not a quicker way than this approach. At the moment (after long discussions) our customer has agreed to go live with **.