Hi Ron,

First of all, I have to say that having blocks inside XhtmlString properties is one of the best features ever! Our editors love it! :)

One way to disable this is to create a custom EditorDescriptor:

[EditorDescriptorRegistration(
    TargetType = typeof(XhtmlString),
    EditorDescriptorBehavior = EditorDescriptorBehavior.ExtendBase,
    UIHint = "MyDescriptor")]
public class MyDescriptor : EditorDescriptor
{
    public MyDescriptor()
    {
        AllowedTypes = new[] { typeof(PageData) };
    }
}

And decorate your XhtmlString properties like this:

[UIHint("MyDescriptor")]
public virtual XhtmlString MyProperty { get; set; }

I'm not sure if blocks inside XhtmlString are officially supported. AllowedTypes attribute used to work with XhtmlString properties, but not anymore.
I've tested the code above with Alloy, EPiServer CMS 9.6.1, and latest version of Google Chrome

Hope this helps!

Excellent that looks like a solid solution! Thanks so much!