Hello @edisilvio
Thank you for contacting the Instructure Community. You can create a rubric criteria worth 0 points that effectively won't count negatively towards a student. However, there is no "don't count this criteria" part of a rubric. You can also leave comments for students or simply not use the rubric for grading purposes and then any criteria you have filled out doesn't automatically count towards their actual grade. Hopefully this is helpful. Here is the Canvas guide:
https://community.canvaslms.com/t5/Instructor-Guide/How-do-I-add-a-rubric-to-an-assignment/ta-p/1058
