Pasting here the AddonsUI.xcu contents, so people can study it quicker:

<?xml version="1.0" ?>
<oor:component-data oor:name="Addons" oor:package="org.openoffice.Office" xmlns:oor="http://openoffice.org/2001/registry" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <node oor:name="AddonUI">
    <node oor:name="OfficeMenuBarMerging">
        <node oor:name="" oor:op="replace">
        <node oor:name="" oor:op="replace">
            <prop oor:name="MergeCommand">
                <value>Remove</value>
            </prop>
            <prop oor:name="MergeFallback">
                <value>Ignore</value>
            </prop>
            <prop oor:name="MergePoint">
                <value>.uno:ViewMenu\.uno:ToolbarsMenu</value>
            </prop>
            <prop oor:name="MergeContext">
                <value>com.sun.star.text.TextDocument</value>
            </prop>
        </node>
        </node>
    </node>
  </node>
</oor:component-data>

I can't comment on it myself. I only confirm that nothing is hidden in current master or version 3.3.0, if I install it.

Uno was change. I don't know if is a normal thing.

This code work :
                <prop oor:name="MergePoint">
                    <value>.uno:ViewMenu\.uno:AvailableToolbars</value>
                </prop>

Yes, using the correct command (.uno:AvailableToolbars) should work. The command was changed in 2004; No idea where did you get the old one.