ldd shows that my /usr/lib64/libmediastreamer.so links to /usr/lib64/libpulsecommon-0.9.22.so. But mediastreamer does have no dependency on pulseaudio, so if I did emerge --depclean pulseaudio was listed as 'can be removed after rebuild of mediastreamer'. Enabled USE-flags for mediastreamer are "X alsa ipv6 speex theora x264".
Created attachment 255827 [details] emerge --info
Thank you for report Markus! Fixed in the tree.