\definefontfeature
  [system:tabnum]
  [system:tabnum]
  [onum=no]

\definefontfeature[default][default][onum=yes]

\setupbodyfont[pagella]

\starttext

\enabledirectives[typesetters.characteralign.autofont]

\bTABLE
\setupTABLE[alignmentcharacter={text->.},aligncharacter=yes,align=middle]
\bTR \bTD 1.23456789 \eTD \eTR
\bTR \bTD 12.3456789 \eTD \eTR
\bTR \bTD 123.456789 \eTD \eTR
\eTABLE

\disabledirectives[typesetters.characteralign.autofont]

\bTABLE
\setupTABLE[alignmentcharacter={text->.},aligncharacter=yes,align=middle]
\bTR \bTD 1.23456789 \eTD \eTR
\bTR \bTD 12.3456789 \eTD \eTR
\bTR \bTD 123.456789 \eTD \eTR
\eTABLE

\stoptext
