Asides from the "Pinned Messages" box (which I really think no one looks at), there should be a way for messages that are pinned to stand out more. For instance:
Which one of these here is a pinned message?
Well, it doesn't matter because there is absolutely no visual indication as to which one it is (it's the second if you really needed to know).
So this post has some value, I at least think a literal pin should be added next to the message or make it highlighted (like when you are mentioned but without the ping) so people can see that it's pinned.