Messaging could cause problems in that it makes it easier for predators to find victims. On the other side of the same equation, not having direct contact or even a way to know who they are, prevents any appearance of impropriety on the part of the overwhelming majority who really are just playing the game.
I do however wish there was a way to put comments on your own town, for example to let people know that you're going to be offline for a time but returning in a week or two.
I also like the pin idea, but only in pinning things you like. Even aside from house farms, some people just don't care what their town looks like. Some may have a temporary area that hasn't been developed yet. Some may simply have a different aesthetic sense than you. What's the point to potentially hurting their feelings?