If you just want to show for an userid, use that then:
HTML Code:
<if condition="$bbuserinfo['userid'] == 'x'">codes</if>
Telling a user that he hasn't activated his account is also done via the first code I have given you or you can use this one.
HTML Code:
<if condition="$bbuserinfo['usergroupid'] == '3'">You haven't activated your account.</if>
3 is the default usergroupid of the "Users Awaiting Email Confirmation".