----
<i>(And here I shall stop; there is of course much more to say. --Brooks Moses)</i>
----
I should also add: there's a set of code for bold math (text and symbols) in [http://www.ntg.nl/pipermail/ntg-context/2004/005314.html this message to the ConTeXt mailing list]and [http://www.ntg.nl/pipermail/ntg-context/2004/005315.html its followup here].