I don't think a CHIRP is the relevant way to report this, as I understand they're primarilt for people to report their own human factors type mistakes. but I do definately feel that this should be reported. I'm assuming that FFF is confident that the cloudbase where he was operating was uniform - no gaps the pilot in question could have been using, and, as has been m,entioned before, that the clearance was for "at" 2000ft, not "not above". The airfield actuals should have been logged - a BKN or OVC for the time in question would go some way to adding credence to the complaint.
The actions of this cowboy have potentially endangered the lives of others as well as himself - by agreeing to take visual separation on traffic he can't see - and as such he does deserve to be chased up and at the very least informed of the error of his ways. I don't think I'm overdramatising that first sentance.
My suggestion would be to contact the ATS provider, supply them with the time of the incident and ask them to check their logged actuals and ATC recordings - then let them take it further if they wish.