\definefontfeature[base][
  mode=node, ccmp=yes, calt=yes,
  liga=yes, dlig=yes, hlig=yes,
  kern=yes, mark=yes, mkmk=yes,
  onum=yes, pnum=yes, salt=yes,
  script=latn,
  ss02=yes, cv01=yes, cv03=yes,
  dlig=yes, cv91=yes]

\definefontfeature[xvicentury][
  ss02=yes, cv01=yes, cv03=yes]

\definefontfamily[mainfont][serif][EBGaramond][features={base, xvicentury}]
\setupbodyfont[mainfont, 9pt] % commenting this does not show the "empty" line

\definemixedcolumns[TwoColumns][n=2, distance=1.5\bodyfontsize]
\definefirstline[bbigline][alternative=line, style=\tfa]

\definebodyfontenvironment[default][a=1.5, x=0.8]

\starttext

\startmixedcolumns

\setfirstline[bbigline] Generation generation generation generation generation % if letter like g p etc ... hanging below base of line "empty" line

\setfirstline[bbigline] Veneration veneration veneration veneration veneration % no empty line

\stopmixedcolumns

\stoptext
