One of the annoyances that has plagued SO chat has been the appearance in the feeds of incorrectly categorized feed items, eg #REbol and red tags from newbie questions on SO.
I just noticed an undocumented API feature which has been exploited here which seems to say that if a room owner posts
/messages/$messageid delete
within 2 minutes, even feed items can be deleted.
I think the simplest way is to do something like this
@rebolbot delete feed
and it deletes the last feed item within 2 minutes of the current time.