This seems to be a recent visual bug. Since recently, the reply button has started appearing in messages you are not able to send messages back to, such as official Roblox messages.
Before this bug that happened since 1 week ago, there was no reply button.
Of course there is an error that happens when trying to send something as fallback but I don’t see that this was a intentional change
Expected behavior
I expect there to be no Reply button, as it was a few weeks back