[Lynne]

Put a condition around all those instances of the join date:

<if conditon="$whatever[userid] != '1'">
The line that $whatever[joindate] is on
</if>

I say $whatever, cuz if it is $post[joindate], then you want to put $post[userid]. If $prepared[joindate], then $prepared[userid], etc.

It's going to be a bit of effort just to hide a joindate. Why not just set it to whatever you want in the usercp?