To my knowledge only public servants should be designated as Public Information officers and his superior may be designated as First Appellate Authority.
The burden of proving that information was furnished rests on PIO and in case of denial, the justification must be done as per clauses Sec.8 or Sec.9 of RTI Act.
What is self-interest has to be defined first? In this query, the applicant was asking the works attended by Panchayat which are in the public interest. There are no exemptions for providing of information if the larger public interest is involved. This personal vengeance, the motive to harass PIO, repeated, frivolous etc., has to be proved by PIO before IC. A procedure has been prescribed that PIO must list out all such applications, date wise, record what was provided as information, and then upload the same in his website and also near the main entrance in the notice board of his office, etc.