Hi Aditya and Gilles,

It seems to me that adding a bar in the margin either with framedtext or with MetaPost, lacks the ability to continue through a page break. Using the ConTeXt built-in sidebar mechanism has the advantage of continuing through a page break, but it is still not perfetct because in some occasions (but not always…) the sidebar plunges into the footnote area. I don't know if the issue can be solved (adding negative bottomoffset solves partly the problem but when there is no footnote then the sidebar appears to be too short…).

Here is an example of how I use the sidebar to enhance \proclaim like texts.

Best regards: OK
%%%% begin test-sidebar-proclaim.tex
%%%%%%%
\definesidebar[ProclaimSidebar]
\setupsidebar[ProclaimSidebar]
	[rulecolor=darkred,
	rulethickness=1pt,
	alternative=2,
	distance=5mm,
%	bottomoffset=-7mm,
%	topoffset=-2mm
	]

\defineenumeration[proclaim]
	[text=,
	before={\startsidebar[ProclaimSidebar]},
	after={\stopsidebar},
	style=slanted,
	title=yes,
	titleleft=,
	titleright={.},
%	alternative=serried,
	alternative=hanging,
%	hang=2,
	width=fit,
	right={~},
	way=bysection,
	prefix=yes,
	prefixsegments={chapter:section}]
%%%%%%%

\starttext

\dorecurse{2}{\input knuth.tex\par}

\input tufte.tex \footnote{The sidebar gets into the footnote\dots}

\startproclaim{Lemma}
\dorecurse{4}{\input ward.tex \par}
\stopproclaim

\stoptext
%%%%%%  end test-sidebar-proclaim.tex