@crogerblair
Most likely, never, as Mozilla engineers really don’t want to give extensions arbitrary read-write access… and I understand them. The feed list is kept in a database; if you want to import an existing feed list, the best way is to make an OPML file with any good converter.
@mikelv
If you’re still interested and the bug still reproduces, could you please share the full URL of the feed (or, for tweetrss.me, the twitter username you’re following in it).
@Kisrah
Sorry for not replying earlier… sounds like Brief had trouble starting some internal components. Are you still struggling with bugs like this one?