In the kitchen, an unofficial complaint discussed verbally or electronically, usually among friends and families, where the issues will never be officially acknowledged and recognized before authorities to address the issues with resolves or solutions. In conclusion, a "kitchen complaint" is as far as the complaint will go, the kitchen.
My son's church youth group were passionate about their complaints after our bible study. Unfortunately, no one thought of contacting their government representatives. The results, only a kitchen complaint, all powerless and emotional.