Users with "mod/forum:postprivatereply" capability cannot view their own private replies when "mod/forum:readprivatereplies" is not enabled

A user with the capability "mod/forum:postprivatereply" but without the capability "mod/forum:readprivatereplies" will be able to post a private reply, but not view their own private reply.

To reproduce:

1. Log in as admin.
2. Go to Site administration / Users / Define roles
3. Edit the non-editing teacher role and remove the "mod/forum:readprivatereplies" capability to it.
4. Save the changes.
5. Go to a forum discussion.
6. Reply to one of the posts p1. Let's call this r1.
7. Reply privately to your reply r1. Let's call this rp1.
8. Reply to another author's post p2 privately. Let's call this rp2.

What happens:

• rp1 is visible to you.
• rp2 is not visible to you.

What I kinda expect:

• If a user has the capability to post private replies but does not have the capability to read private replies, the user should at least be able to see the private replies that he/she posted.