8

You can disable the stickyness via your settings under 'Preferences':


4

Yes, people have been noticing this on all sites throughout the Stack Exchange network. There's a 'central' bug post on the Main Meta which has now been marked status-completed, meaning it should be resolved.


3

Yes, this is the so-called Custom Filters feature, which has been released today after being alpha-/beta-tested for almost a year as Custom Question Lists. You can find most information you're looking for in the first link, which leads to the announcement of the feature on Meta Stack Exchange.


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