[Bug]: Closed discussions do not reflect on already open comments

From Sam Jenkins:

> Via a complaint by a reader we have picked up an an issue with the discussion platform which I have confirmed via a test.
>
> What the user complains of is this: even after comments on a thread have been closed, they are able to click "reply" under other user's comments, get a text box, type out their comment and then have it rejected because the thread is closed. This doesn't just affect anyone unlucky enough to have started typing out at reply before comments close, but anyone who has not refreshed the page since comments have closed.
>
> Obviously, the "reply" buttons cannot spontaneously disappear at thread closure without a browser refresh on the user's end, but ideally users should be informed comments have closed at the point that they click "reply", rather than at the point of submission of their post.
>
> I've no idea if there is a feasible fix to this, but we did want to make you aware as it can understandably be very frustrating to users.