Wouldn't showing that just to moderators be enough?
Probably, but then you have the other side of the equation which is that some users could spam karma to each other for no reason other than to appear important. Again moderators would be aware of this if they bothered to check but no one else would be the wiser so would have no reason to bring it to a moderator's attention. I've seen no real evidence of this, I'm just trying to postulate possible justifications for the current system.
Personally I've not felt a need for karma to be anonymous but on the other hand I can understand that someone might want to make an anonymous 'gift'. Prior to this I would usually add my name so they knew who it was from and this leaves it up to the user's discretion. Assuming a responsible set of forum goers which I do believe is the prevalent case (at least on the GalCiv2 site) I see no harm in this.
However, I'm not the one you need to convince. Karma is handled the same on all sites and I'm not sure that what would be fine for GalCiv2 would also be fine for WC plus that means that this probably is really an All Forums issue versus a GalCiv2 site specific issue.
The thing is that this is more of a feature request or at the least a request for a justification as to why features were changed without notice or comment as opposed to some site specific or all forum bug/problem. The fact that Andrew hasn't yet commented also doesn't hold out much hope that this is considered significant, but perhaps he just took a weekend off.
I would say that if you feel strongly about it that you should probably open up a Forum Issue about it. You know as well as I do that it's unlikely to change the status quo, but at the very least you have a legitimate question that deserves an offical response as to why it's felt the new system is better.
There's no reason to be afraid of submitting a forum issue as long as proper protocol is followed. Just remember these four simple steps.
1. Once you enter the shop move immediately to the right.
2. Order your soup in a clear loud voice, but not too loud.
3. Place your money on the counter with your right hand and move laterally to your left.
4. Take your soup and leave the shop without comment.
In the immortal words of Foghorn Leghorn "It's a joke son, a joke".