[Therion] Underscore coming out as period in legend comment

When using map-comment if you put an underscore in it comes out as as period (.) I am trying to include a web address that includes underscore. Metapost tells me that \textunderscore or \_ but that only works in metapost /comment, which is a bit of a pain, and not in map-comment directly. Is there a way of using it directly in map-comment? thanks Andrew