I can probably shed some light on why the PRIV function on the Caledonian Sleeper site was removed. As
@user1234 says here:
...this was a longstanding oddity.
I run a (fairly large) YouTube channel focusing on air and rail travel, and I often get messages from people who’ve seen a good deal on a fare and want to share it.
In December, I got at least a dozen messages from various enthusiasts out of the blue, saying they were travelling on PRIV codes, sometimes extensively, masking the discount by adding their 16-25 or Disabled railcard to the booking.
Because I work for Network Rail, who keep an eye on what I do outside work and bind me to an ethics policy, I felt duty bound to report this to Caledonian Sleeper (who are basically a customer of NR).
From the messages I was sent it was obvious that a large pool of people were misusing the discount deliberately and repeatedly, evading thousands of pounds worth of fares.
I was also sent messages, and had conversations with at least two people who were actual rail staff and Priv holders who encouraged me to abuse the discount. I know who these people are and where they work, because it says so all over their social media.
These people know who they are and they have spoiled it for everyone, as well as put me in a difficult position. Well done.