I can not imagine why this function will behave differently. Especially when planned evasion in CF 10. Probably you are calling it from a tag CFINPUT?
<cfinput id="foo" value="#htmlEditFormat(someValue)#" />
If so, then in CF6 - CF9 this tag automatically uses HTMLEditFormat()for values. Calling a second instance HTMLEditFormat()does not affect the output. But CF 10+ updated the tag to use encodeForHTML()for values. If you also chose HTMLEditFormat(), then you encode the output twice.
HTMLEditFormat() encodeForHTML(), (CF10 +). ColdFusion 11, HTMLEditFormat() ColdFusion 12, .
HTMLEditFormat() 4 : <, >, &, ".
encodeForHTML() , UTF-8. "encodeFor" , (html, htmlattribute, js, css, xml ..).