The host list to which you refer is on the BOINCstats side of things; all of this information is imported from the projects. Nothing can be changed by BOINCstats because it would just change back during the next update--the only exception being "retired" projects, where you are allowed to update your CPID through BAM.
There are a couple of scenarios where this may happen; if the hosts in question are mobile and change networks a lot, there is currently an issue with the recent builds of BOINC where the projects will change some host information every time you change networks. Because the projects update at different times with BOINCstats, it looks like there are duplicate hosts. However, if you look at the host details you will notice that the duplicate hosts do not share any common projects. This will go away if you stay on the same network for a while, and all the projects have a chance to sync with BOINCstats. Unfortunately, there is not a fix from the BOINC client team for this yet.
The other scenario is similar, where projects you no longer crunch for don't receive updated host information (such as host CPID) and appear as different hosts on BOINCstats. If you look at your "duplicate" hosts and notice one with your current projects, and one or more with older projects this is probably what's happening. To solve that, you simply must attach the host to all of your projects you want to line up (no work needs to be done, they just have to connect) and give it a day or two to update on the BOINCstats side.
I suspect your last scenario is what caused the mishap on BOINCstats. Unfortunately, the host in question was recently sold, so that host can no longer connect to BOINCstats. In a way, it is really not that big a problem: it is not as if I lost credit, so the duplicate hosts are not that big a deal, only that it is not as clean on my host page.
Also, I suspect another bug might be related so I will ask here rather that create a new thread. When I sync with BOINCstats on my two currently running hosts, all of my project resources are at the default level on the project resources page, not the resource share that I have in my separate host list page. The two hosts in question have been crunching for over a week or so, so everything should line up and sort itself out by now I should think.
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