Short names

A single-character name tells a reader nothing about what it holds. At the use site a binding is just $f, and every reader of the template has to go back to the declaration to learn what it is for.

Incorrect:

<xsl:template name="indent">
  <xsl:param name="d" as="xs:integer"/>
  <xsl:value-of select="string-join((for $i in 1 to $d return '  '), '')"/>
</xsl:template>

Correct:

<xsl:template name="indent">
  <xsl:param name="depth" as="xs:integer"/>
  <xsl:value-of select="string-join((for $i in 1 to $depth return '  '), '')"/>
</xsl:template>

The check covers xsl:variable, xsl:param, xsl:template, and xsl:function, and measures the local part, so eo:k is as short as k. An xsl:with-param is left alone, since its name is fixed where the parameter is declared.