XE core 1.5.4.2 기준으로
module/member/skins/default/modify_info.html 수정 (기본 스킨을 사용할 경우)
<div class="a" cond="$formTag->name != 'signature'">{$formTag->inputTag}</div>
<div class="a" cond="$formTag->name =='signature'">{$editor}</div>
이 부분을 아래와 같이 수정
<div class="a" cond="$formTag->name != 'signature'&&$formTag->name != 'user_name'&&$formTag->name != 'nick_name'">{$formTag->inputTag}</div>
<div class="a" cond="$formTag->name =='signature'">{$editor}</div>
<div class="a" cond="$formTag->name =='user_name'"><input type="text" name="{$formTag->name}" value="{$member_info->user_name}" disabled="disabled" /></div>
<div class="a" cond="$formTag->name =='nick_name'"><input type="text" name="{$formTag->name}" value="{$member_info->nick_name}" disabled="disabled" /></div>