Checking permissions or customising Forums module

I'm new to Sitefinity and .NET. I'd like to customise Forums module from Sitefinity 8.0, so that only moderators can create new threads, and that ordinary users (who don't have a right to create a new thread) won't get a "New thread" link at all. I've modified the permissions for that (following docs.sitefinity.com/forums). However, ordinary users still get "New thread" link, but that link fails for them. Instead, I'd like not to show that link at all.

I have a custom template for my Forums gadget > Edit > Advanced > ControlDefinition > Views > ForumsFrontendPostsList > TemplatePath and it is being used. How do I check in the template whether the user can create a new thread?

Also, I've created a custom class

namespace SitefinityWebApp.MyPackage.Forums
   public class PostListView : Telerik.Sitefinity.Forums.Web.UI.PostsListView
      public PostListView()
         var unusedVariableJustToSetAbreakpoint = 1;
    
  

and but I don't know how to check permissions in it. Also, I don't know where to register that class (I looked at Administration->Settings->Advanced-> Forums > Controls > Create new). When I put that class namespace and class name to Forums gadget > Edit > Advanced > ControlDefinition > Views > ForumsFrontendPostsList > ViewType (replacing the original Telerik.Sitefinity.Forums.Web.UI.PostsListView) and I save it, it gets reverted back.

Please advise (with a code snapshot if it needs custom code).