Hi It turns out that MoreLikeThis handler does not use queryTime synonyms expansion.
It is only compatible with indexTime synonyms. However multiword synonyms are only compatible with queryTime synonyms expansion. For this reason this does not allow the use of multiword synonyms within together with the MoreLikeThis handler. Is there any reason for the MoreLikeThis feature not compatible with Multiword Synonyms ? Thanks -- nicolas