On second thought, not sure resampling |S| words from L is a good idea because you want 100% coverage of your sentiment universe and an asymmetrical corpus is n

On second thought, not sure resampling |S| words from L is a good idea because you want 100% coverage of your sentiment universe and an asymmetrical corpus is not a priori incorrect so resampling does not solve anything except reweighting match lists which may not even lead to symmetrical sentiment since the distribution of words amongst the language (TF-IDF helps here) is not necessarily the same in your negative and positive lists