Is there a forum for code design critique and suggestions?

...and by forum, this area is named UnityAnswers. There's a different place labeled "Forums" (left side of the top bar.) Unlike Unity Answers, the Forums area is divided into specific topics. Scripting is one.

But in practice the HelpRoom area is common for general code Q's. It's here in Unity Answers (by your Question, "Spaces" should have a dropdown. with HelpRoom as one option.) There's often more traffic there, or at least different people reading it.