Problems with Build trigger, commits during mvn release:prepare triggers next build

We want teamcity to build a new release everytime a developer commits a change in our release branch. Unfortunately the commits executed during the release run trigger the next build.
We tried several variations of VCS Trigger rules, but nothing seems to help.

We tried to filter on the user name "appadm"
we tried to filter on the comment "maven-release-plugin"
we tried a combination of both

we initially had a quiet period of 1800

but anyway the build is triggerd of commit like :

This smells like a bug to us. We are using TeamCity Enterprise 6.0.2 (build 15857)

Our VCS Settings

VCS root (slightly anonymized)


and the build trigger infos :


we also tried
-:user=appadm:**/*

Please help if you have any idea whats wrong.

Thanks in advance, Oli