Delete all articles in feed fails: deleted articles re-appear


I want to clean-up my feeds, clearing all read/not starred articles in a feed. As I was told that Feedreader was all about smartfeeds, I made a smartfeed matching all rules:

  • Feed name is xxx
  • Status is Read
  • Flag is not Starred

Then Smartfeed > CRTL+A selects all articles > "Delete" to erase all articles. It works (I cannot see any remaining articles), but if I go to another feed and comeback to that smartfeed, then I can see old articles re-appear (maybe 90% of articles get deleted, but 10% re-appear). I tried many configurations (check/uncheck "Group similar articles", Group by Date / no grouping, classic/wide/full layout) and got the same bug in all cases. The only way to get 100% rid of articles in the smartfeed was to delete the reappearing articles 1 by 1 by hand.
FYI, the feed I tried this for is
http://service.openkapow.com/ppow/rmfic?max=40&rssVersion=2.0&channelName=&channelLink=&channelImageURL=&channelDescription=
(you need to increase httpConnectionTimeout and httpReadTimeout at least to 180s). Note: wait for a couple of days until some "similar articles" are grouped.
This is a serious bug, because I can't erase all read non starred articles. Could a developper handle this bug and first tell me if he/she could reproduce the problem?

Articles re-appear in normal feeds too

This does not occur only with smartfeeds.
Try this feed: http://feeds.seesmic.com/public.timeline.rss
CTRL+A to select all articles in the wide view, then "Delete" to delete them.
CTRL + A then "delete": "100 unread" becomes "31 unread" (should be zero) - but article list pane is cleared.
Then again CTRL + A then delete: "31 unread" becomes "11 unread" (should be zero).
Then again CTRL + A then delete: "11 unread" becomes "5 unread" (should be zero).
Then again CTRL + A then delete: "5 unread" becomes "3 unread" (should be zero).
etc.
What is the problem? Why do all feed articles not get deleted in the first place?