So if I create a query in the BaseX 9.3.2 GUI, thus:

declare function local:processMatch($in as text(),$matchPattern as xs:string) as item()+ {  
  let $search as element() := analyze-string(normalize-space($in),$matchPattern)
  return $search
};

let $example := <para>These are a bunch of words, and some of the words are <em>special</em> words.</para>

for $text in $example//text()
          return local:processMatch($text,'bunch|special')

I get:

<fn:analyze-string-result xmlns:fn="http://www.w3.org/2005/xpath-functions">
  <fn:non-match>These are a </fn:non-match>
  <fn:match>bunch</fn:match>
  <fn:non-match> of words, and some of the words are</fn:non-match>
</fn:analyze-string-result>
<fn:analyze-string-result xmlns:fn="http://www.w3.org/2005/xpath-functions">
  <fn:match>special</fn:match>
</fn:analyze-string-result>
<fn:analyze-string-result xmlns:fn="http://www.w3.org/2005/xpath-functions">
  <fn:non-match>words.</fn:non-match>
</fn:analyze-string-result>

The trailing space after the are in the second fn:non-match element is gone.

Should that happen?  Can I make it stop happening by invoking the function differently?