Small Messaging Bug

It's not a big issue, it's just a little irritating. The bug stops my client from realizing that I have seen a message sent by a friend, and so will continue to flash as if I have not read the message. I can manually stop the flashing though if I mute the conversation and then unmute. If it's not actually a bug and instead I managed to mess up some setting in the settings, then if someone could notify me that would be great.