While browsing through mutt's manual I stumbled upon this:
~H EXPR - messages with a spam attribute matching EXPR.
After reading up on the spam tags I have changed my configuration to
include
spam "X-Spam-Score: .*\\(\\+\\+" sa2
set index_format="%4C %Z %{%b %d} %-15.15F (%4c) %?H?[%H] ?%s"
This improves my mail handling a lot. I can limit my view to ~H sa2 to bulk-move the spam in my inbox to the bayes-learn-spam folder. And false positives are easily discernable since possible spam (i.e. something marked with X-Spam-Score: 3.0 (+++)) is tagged with sa2 in the folder index:
27 Nov 04 jetlik jetlik (2,8K) [sa2] SpecMoney stock