Good afternoon.
I just wanted to report that, after either rating up or down someone in a locked thread, I found that the "Reply to this" button would appear.
I don't know if this is a known issue, since I didn't found any reference of it within the stickies nor in the latest 3 pages of the Site Feedback forum. If it is a known issue, I am sorry for taking your time.
Have a nice day~!
Kind regards,
Amrik.