> 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