> why  use math here?

It was to avoid oldstyle figures that I use by default. But finally it's
better to use oldstyle figures even in tables.

Another question about fonts. Is there a way to define a conditional
mathcommand based on the current alternative style? For instance, in the
following example I would like to keep the bold effect but with adaptation
to the local alternative style (in text mode, when the local alternative
style is \tf I would like the mathcommand to be \bf, when it is \it I would
like \bi, when it is \bf I would like \bf and when it is \bi I would like
still \bi):

\starttext
\definemathcommand[cool]{{\bfmath cool}}
text mode normal: \cool\crlf
text mode italic: {\it \cool}\crlf
text mode bold: {\bf \cool}\crlf
text mode bolditalic: {\bi \cool}\crlf
\stoptext