One of the changes in this set removed the ability to mark messages to yourself as unread. Given that I cannot mark them as unread, I am unable to test if marking as read also has the same problem.
You should be able to exclude the 4 changesets that went along with my pull request from the possible culprits because I'm quite certain I tested my changes using messages to myself, and hence why I noticed this behavior in the first place.
Modmails too. They wont leave the unread section of the inbox despite not actually being unread.
@aperson I am not able to reproduce the functionality you describe. I do have some mod-mail messages that I apparently cannot mark as unread, however, they all appear to be ban messages.
Yes, ban messages are what I'm referring to. I'm not sure if it happens with normal (mod -> user) messages.
Ban messages no longer seem have any problem with being (un)marked as read.