The thread I saw go south yesterday happened when the discussion went from talking about the trains themselves, and turned to people talking about people.
As long as the discussion sticks to the trains then it should go well. Oftentimes things go badly when people take a critique of models and transfer that critique to themselves.
If someone opens a thread and draws a comparison between the prototype and a model then I think the critique of the model should be allowed. If someone opens a thread and gives the opinion that the model is great for reasons a,b, or c, then others should be able to give the opinion that the model has flaws with x,y, or z.
In a different scenerio, if someone is simply posting a photo of their toy or model to show off then the critique really isn't warranted in my opinion.
