\definetextbackground[underline]    [location=text,alternative=1,background=,frame=off]
\definetextbackground[overstrike]   [location=text,alternative=2,background=,frame=off]
\definetextbackground[exlines]      [location=text,alternative=3,background=,frame=off]
\definetextbackground[strikethrough][location=text,alternative=4,background=,frame=off]

\definestartstop [underline]
  [before={\starttextbackground[underline]},
   after=\stoptextbackground]

\definestartstop
  [overstrike]
  [before={\starttextbackground[overstrike]},
   after=\stoptextbackground]

\definestartstop
  [exlines]
  [before={\starttextbackground[exlines]},
   after=\stoptextbackground]

\definestartstop
  [strikethrough]
  [before={\starttextbackground[strikethrough]},
   after=\stoptextbackground]

\definetextbackground
  [sideline]
  [mp=mpos:region:sideline,
   location=paragraph,
   framecolor=red,
   frameoffset=5mm]

\definestartstop [sideline]
  [before={\starttextbackground[sideline]},
   after=\stoptextbackground]

\starttext

    \startunderline     \input tufte \stopunderline      \blank
    \startoverstrike    \input tufte \stopoverstrike     \blank
    \startexlines       \input tufte \stopexlines        \blank
    \startstrikethrough \input tufte \stopstrikethrough  \blank
    \startsideline      \input tufte \stopsideline       \blank

\stoptext
