This minimal example:
\starttext
\currentdate-\currenttime\quad\ConTeXt-version=\contextversion\blank
Testing \ConTeXt macro\ \tex{inmargin}
\blank
Some text to fill the body of the text.\par
\inmargin{\hbox{abc}}
Some text to fill the body of the text\par
\stoptext

produces an underfull hbox:

Underfull \hbox (badness 1210) in paragraph at lines 6--6
 [][][]

the same happens with the line: \inmargin{abc}
Underfull \hbox (badness 1210) in paragraph at lines 6--6
 []<9: lmroman12-bold @ 12.0pt> abc[]

addition of \hfil or \hss doesn’t help.

My conclusion: this is somewhere located in \inmargin. It would be nice if this can be resolved, because in procession some 500 \inmargin’s the log is cluttered with all these messages.

dr. Hans van der Meer