Pinning a private message makes it public

When users post on our forum I create a ticket on github. I then like to add the github ticket URL to the forum post as a private message so I can easily know the reported issue has been added on github.

I noticed that when I try to pin a private message it makes it public! Please check this as it isn't a desired behavior. The reason I want to pin the private message is so I can quickly see the URL pointing to the github ticket.