Hi Naoko,
As you may be aware, there's no provision in a translation memory to penalise a single segment so I don't quite see how we could implement such a feature as penalizing segments from a particular TM. The best solution I can imagine is that the segment is given an attribute to indicate which TM it came from and then, in SDL Trados Studio, you can apply a filter and set a penalty for those segments. Does this sound like a reasonable approach?
Thanks,
David