When looking at community solutions, I often see text that says “Write a comment” and immediately below it it says, “Comments have been disabled.” I think it would make more sense to not display the comment section at all if comments are disabled.
On the other hand, “Comments have been disabled” lets people know that the user has intentionally disallowed comments 
In any case, it doesn’t make sense to display the “Write a comment” text if comments are disabled.
I see where you’re coming from.
Not displaying it at all won’t do what you want it to do. If people are used to seeing the comment section and then on some pages it’s missing, it will appear broken instead of disabled. So the choice here was likely to have consistent page layout.
That said, I think Write a comment can be removed, and then it’s like youtube:
3 Likes