Just checked here in
ConTeXt  ver: 2010.03.20 22:59 MKIV  fmt: 2010.3.21  int: english/english
Can confirm that:

\starttext
sonder\underbar{bar}

gives vertical bar, but the following (note the blank line after starttext) does not.

\starttext

sonder\underbar{bar}

met vriendelijke groet
Hans van der Meer




On 22 mrt 2010, at 21:06, Peter Rolf wrote:

Hi,

the underbar line is drawn vertically here.

\starttext
sonder\underbar{bar}
\stoptext

MTXrun | current version: 2010.03.20 22:59
This is LuaTeX, Version beta-0.53.0-2010032213 (rev 3535)

Peter
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