This is not the first time this has been requested.
Would you want this on the MS_Description property, though?
My inclination is to use HTML_Description, or BBCode_Description, or RTF_Description and then put a plain text description on MS_Description. So in your database you would have two properties automatically set by SQL Doc:
HTML_Description property is "This is <b>important</b>"
MS_Description property is "This is important"
This is not unlike how formatted emails work.
This would avoid breaking compatibility with other tools which read this and already existing descriptions that say e.g. "This constraint checks 0<b and 10>b".
Would that make sense for you? Or would that annoy you?
Red Gate Software