The adjudicated incompetent cannot initiate legal proceedings in his own name, but the rules of civil procedure allow for liberal amendment of pleadings to correct mistakes, and I can't imagine any small claims magistrate would deny amendment of the complaint, permitting the guardian to sign. It is a technicality, and the defendant, who would have notice of the allegations, would not be prejudiced. If the case were dismissed, it would take only a matter of minutes to re-file the complaint with the proper signature.
If you are the defendant, you may be able to use this to create delay, but it will not result in a final disposition of the claim in your favor.
Mr. Huddleston is an Ohio-Certified Specialist in Estate Planning, Trust & Probate Law, with offices in Columbus and Dayton, serving client families throughout Ohio. He may be contacted directly by phone toll-free at 888.488.7878 or by email CLH@HUDDLAW.COM. Mr. Huddleston responds to Avvo questions as a public service to help educate and provide general guidance to questioners, but his responses are not legal advice and do not create an attorney-client relationship.