Add the related list Attached Knowledge to the incident form, then agents can select the record, delete it and Update the incident to remove the link between Incident and the knowledge article.
I've just tried the solution above (provided by Sanjiv Meher) in my own instance, it works fine, i think it's an easy and acceptable solution to apply!
If I have answered your question, please mark my response as correct so that others with the same question in the future can find it quickly and that it gets removed from the Unanswered list.
Thank you
Cheers
Alberto
