Indeed. I should have known better. Temporary attack of brain weakness, I suppose. For those who want to see for themselves, the minimal example below will do.

dr. Hans van der Meer

% test character entity.
\startxmlsetups demo:entity
	\xmlsetsetup{#1}{root}{demo:entity:*}
\stopxmlsetups
\xmlregisterdocumentsetup{demo}{demo:entity}
\startxmlsetups demo:entity:root
	\blank Start test:\crlf
	flushing: \xmlflush{#1}\crlf
	End test\blank
\stopxmlsetups
\startbuffer[demo]
<?xml version="1.0" encoding="UTF-8"?>
<root>amp = &amp; and #38 = &#38;</root>
\stopbuffer
\starttext
\currentdate-\currenttime\quad\ConTeXt-version=\contextversion\blank
{\bf Testing use of character entities}\blank
These should produce the same result: \type{&amp;} and \type{&#038;} and indeed they do.\blank
\xmlprocessbuffer{demo}{demo}{}\blank
\stoptext



> On 19 Apr 2018, at 14:44, Hans Hagen <j.hagen@xs4all.nl> wrote:
> 
> On 4/19/2018 10:53 AM, Hans van der Meer wrote:
>> The following use of character entities &#038; aborts in ConTeXt. That is of course because the # is seen as a parameter. Changing this to &\#xxx; or &\letterhash xxx; typesets &#038; as is, but that is not the intention, because an ampersand should appear. So, how do I proceed here?
>> Minimal example:
>> % test character entity failure.
>> \startxmlsetups demo:entity
>> \xmlsetsetup{#1}{root}{demo:entity:*}
>> \stopxmlsetups
>> \xmlregisterdocumentsetup{demo}{demo:entity}
>> \startxmlsetups demo:entity:root
>> \blank Start test:\crlf
>> root: <amp> = "&amp;"\crlf
>> root: <number> = "&\letterhash 038;”\crlf % &\#038; produces the same
>> End test\blank
>> \stopxmlsetups
> 
> you are tex mode there so & == &
> 
> 
>> \startbuffer[demo]
>> <root></root>
>> \stopbuffer
>> \starttext
>> \currentdate-\currenttime\quad\ConTeXt-version=\contextversion\blank
>> {\bf Testing use of character entities}\blank
>> These should produce the same result: \type{&amp;} and \type{&#038;}\blank
>> \xmlprocessbuffer{demo}{demo}{}\blank
>> \stoptext
>> dr. Hans van der Meer
>> ___________________________________________________________________________________
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