First (left) I expected this (the fat lines I added) . The edges of arm assets that touch file edges are invisible when creating new bone and they should be visible. If the asset had no alpha channel (whole file filled), I wouldn't see the selection at all
2nd (right), then I think it's a bug. Whether it's checked or not, I don't see unselected vertices weights.
It was something like this before (photoshopped):
When weights tool is ON but no verticle is selected I can see the smal lcircles, but when I select any verticle, the other circles disappear.
For the last problem, I don't know when it occured. π But I'm sure the filter was not on, I tried all the things in header of hierarchy panel. It may look like it was on, but back then I had no assets under these bones. It didn't appear even when I selected bones. Anyway I think i doesn't disappear even when the filter is on, it just shows bone options instead of attachment.