Produce HTML entities when using XSLTTag(s): XML
You disable the automatic output escaping and use the & entity to build the actual entity.
<P><span style="border-style:solid;border-width:1px;"> <a href="{link}"> <xsl:text disable-output-escaping="yes">&nbsp;&rArr;</xsl:text> Read the article</a>. <xsl:text disable-output-escaping="yes">&nbsp;</xsl:text> </span> </P>