I don't think this is a good idea. The structure of the site means that every new user is already globally ignored, because they have no followers. A primary way for new users to get noticed and to get followers is through the global feed. I think the costs of allowing people to block them during those crucial first few days of membership sends the wrong message, and encourages an insulated culture that seems very antithetical to how I envision hubski.

I see what you're saying that simply having the feature available does not mean that everyone will use it. The problem is, if the feature is available, it's likely that there will be less work done on substantial and effective strategies to integrate new users and prevent junk posts (like ButterflyEffect's suggestion in your other thread). If it happens that this feature becomes popular, especially among the influential users with many followers, it will affect the initial impression users have when they come to the site.

If I'm reading you right, your main complaint is that global is full of junk posts right now. Well, I think my response is 'deal with it.' The natural consequence of a global feed is that it will show the good with the bad. There's a reason they were called "The knights of /new" on reddit. Browsing a global feed is not always pretty, especially when there's an influx of new users. But letting people block all new users entirely throws out the baby with the bathwater in my opinion. We only have a couple days to keep new users interested, and if they feel like their contributions are not being noticed or appreciated, they will not stick around, with good reason.