This should work
coreFunctions::sendHtmlEmail(SITE_CONFIG_REPORT_ABUSE_EMAIL, $subject, $htmlMsg, SITE_CONFIG_REPORT_ABUSE_EMAIL, strip_tags(str_replace("<br/>", "\n", $htmlMsg)));
coreFunctions::sendHtmlEmail($reported_by_email, $subject, $htmlMsg, SITE_CONFIG_REPORT_ABUSE_EMAIL...