not a cache issue in terms of the Activity Feed...

steps taken:

logged in

found a random nude image

went to person's activity feed and bookmarked page

logged out

cleared cache

closed browser

opened browser

used bookmark without logging into the site at all

my results are captured below, and as you can see nudity is quite visible there.  it's been this way from the start of the whole activity feed.

if i am logged out and IN the galleries, the nudes won't show, same as having the filter on in my prefs; however, Activity Feed does not follow the same rules - you still see whatever thumb was made for the galleries without any alert that there is nudity if the thumb itself is devoid of nudity.  i'd assume it's the same for any of the gallery flagging features.. shrug...