I am told that many municipalities check listings for statements such as _________ updated recently and than check if the house had proper permits for that update. If the permits don't exist, a violation is cited. Better not to brag about what may not be legal. Just a suggestion. By the way, we at Lieb at Law always recommend doing everything by proper permit.
To illustrate, we just spent 6 months navigating the Historic Society and Building Department just to get 2 new signs on our building. I just believe disclosure about liability for those who have not complied is necessary. Good luck.