I see another issue that hasnt been raised just yet, so I will point it out.
Let us assume you do something in a thread, since the cooking example has been going on I will use that. You make a wonderful batch of cupcakes and everyone loves it. But, then later in the thread you out of your way to make sure no one knew it was you who made the cupcakes? The issue in this case is that the single skill or reputation point has to be evaluated and reevaluated constantly throughout the thread. So first you have a point, then you take away a point, then maybe you get two points and then get really sneaky and stave off those points. This is going to make the complicated process of grading already harder.
To add my voice to what others have said, from the perspective of an ST, if a PC is becoming prominent we know. There's no PCs in any domain that the ST isn't aware of being a mover and shaker. In the same train of thought, other PCs tend to be very aware of this as well OOC. I don't really see this adding anything.
And as a final problem, I would point out that there is an assumption in this idea that is problematic. The Idea of a reputation system, whether good or ill, assumes that PCs want to be known. Sure in some cities making a name for yourself is great, but in others? For example in Sahova, you do not want to become known to the general populace unless you are making a huge power grab. Anonymity is a shield, and when you bust it you have to deal with severe consequences. That should be a conscious choice on the part of a PC, in my opinion, because it can be such a game changer in many places.
Edit: I mention this because it came up a lot and I didn't address it. I am actively against systems like shield points. If it works for another city more power to you, but I do not want them in my domain, not at all.
Let us assume you do something in a thread, since the cooking example has been going on I will use that. You make a wonderful batch of cupcakes and everyone loves it. But, then later in the thread you out of your way to make sure no one knew it was you who made the cupcakes? The issue in this case is that the single skill or reputation point has to be evaluated and reevaluated constantly throughout the thread. So first you have a point, then you take away a point, then maybe you get two points and then get really sneaky and stave off those points. This is going to make the complicated process of grading already harder.
To add my voice to what others have said, from the perspective of an ST, if a PC is becoming prominent we know. There's no PCs in any domain that the ST isn't aware of being a mover and shaker. In the same train of thought, other PCs tend to be very aware of this as well OOC. I don't really see this adding anything.
And as a final problem, I would point out that there is an assumption in this idea that is problematic. The Idea of a reputation system, whether good or ill, assumes that PCs want to be known. Sure in some cities making a name for yourself is great, but in others? For example in Sahova, you do not want to become known to the general populace unless you are making a huge power grab. Anonymity is a shield, and when you bust it you have to deal with severe consequences. That should be a conscious choice on the part of a PC, in my opinion, because it can be such a game changer in many places.
Edit: I mention this because it came up a lot and I didn't address it. I am actively against systems like shield points. If it works for another city more power to you, but I do not want them in my domain, not at all.