[Lynne]

Are you trying to hide *your* activity or every admin's (ie. user in usergroupid 6) activity from other users?

If yours, you can try:

<if condition="$bbuserinfo['userid'] == '2'">
the line to hide from all except userid 2
</if>

or if for usergroup:

<if condition="$bbuserinfo['usergroupid'] == '6'">
the line to hide from all but usergroupid 6
</if>

Try that and see if it works.