I would recommend also unsetting block name "wishlist.sharing" as without doing so the wishlist can still be reached by url http://www.yourmagentowebsite.com/wishlist/index/share/1234/ and could be exploited by spammers (1234 is wishlist ID).
Comment out the following in wishlist.xml like so:
<!--<block type="wishlist/customer_sharing" name="wishlist.sharing" template="wishlist/sharing.phtml" /> -->
or add this in your local.xml:
<wishlist_index_share translate="label">
<reference name="my.account.wrapper">
<action method="unsetChild"><name>wishlist.sharing</name></action>
</reference>
</wishlist_index_share>