Drat... Not using Radar annoncements myself (I find them too spammy), I did not notice this...
This bug is not related to the new Lua feature, but to an optimization I made: the friend and muted status are cached for each avatar in the list instead of being re-checked each time the list is refreshed, but as a result the Radar also observes mute and friend lists events and rebuilds the list each time one such event is triggered... A refresh (instead of a full list clearing and rebuild) is needed, to avoid the announcements.
It will be fixed in next releases. In the mean time, and if you build the viewer yourself, you can change the HBFloaterRadar::onChange() method in indra/newview/hbfloaterradar.cpp to read: