var banned = ['ユーザ名1', 'ユーザ名2', '…'];

$ cat ubuntu-ja-ban-users.user.js
// ==UserScript==
// @name           ubuntu-ja-ban-users
// @namespace      http://localhost/
// @description    Hack for Ubuntu Japanese Forum, Hide some Users
// @include        https://forums.ubuntulinux.jp/
// @include        https://forums.ubuntulinux.jp/index.php
// @include        https://forums.ubuntulinux.jp/viewforum.php*
// @include        https://forums.ubuntulinux.jp/viewtopic.php*
// ==/UserScript==
(function(){
    var banned = ['einundzwanzighundertsechs'];
    var censored = '<span style="color:gray">censored</span>';
    function foreach(id, inner, outer, proc)
    {
    for (var i = 0; i < banned.length; ++ i)
        {
        banned[i] = inner(banned[i]);
        }
    var nodes = document.evaluate(outer(banned.join(' or ')),
                      document.getElementById(id),
                      null,
                      XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
                      null);
    for (var i = 0; i < nodes.snapshotLength; ++ i)
        {
        proc(nodes.snapshotItem(i));
        }
    }
    function enclose(prefix, suffix)
    {
    return function(x) { return prefix + x + suffix; };
    } 
    function censor(x)
    {
    x.innerHTML = censored;
    }
    switch (location.pathname)
    {
    case '/':
    case '/index.php':
        foreach('idx1',
            enclose('span="by ', '"'),
            enclose('//td[@class="tcr" and span/@class="byuser" and ',
                ']'),
            censor);
        break;
    case '/viewforum.php':
        foreach('vf',
            enclose('.="by' + String.fromCharCode(160), '"'),
            enclose('//td[@class="tcl" or @class="tcr"]//span[@class="byuser" and ',
                ']/parent::*'),
            censor);
        break;
    case '/viewtopic.php':
        foreach('punviewtopic',
            enclose('.//a="', '"'),
            enclose('//div[@class="postleft"]/dl[', ']'),
            function(x)
            {
            x.innerHTML = censored;
            x.parentNode.nextSibling.nextSibling.innerHTML = censored;
            });
        break;
    }
})();

$ cat ubuntu-ja-censor.user.js
// ==UserScript==
// @name           ubuntu-ja-censor
// @namespace      http://localhost/
// @description    Hack for Ubuntu Japanese Forum, Hide some Topics and Users
// @include        https://forums.ubuntulinux.jp/
// @include        https://forums.ubuntulinux.jp/index.php
// @include        https://forums.ubuntulinux.jp/viewforum.php*
// @include        https://forums.ubuntulinux.jp/viewtopic.php*
// ==/UserScript==
(function(){
    var banned = ['einundzwanzighundertsechs'];
    var censored = '<span style="color:gray">censored</span>';
    var blocked = eval(GM_getValue('blocked', '[]'));
    function getNodes(list, from, outer, inner)
    {
    if (list.length == 0) return { snapshotLength: 0 };
    var a = [];
    for (var i = 0; i < list.length; ++ i)
        {
        a.push(inner(list[i]));
        }
    return document.evaluate(outer(a.join(' or ')),
                 from,
                 null,
                 XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
                 null);
    }
    function foreach(from, outer, inner, proc)
    {
    var nodes = getNodes(banned, from, outer, inner);
    for (var i = 0; i < nodes.snapshotLength; ++ i)
        {
        proc(nodes.snapshotItem(i));
        }
    }
    function enclose(prefix, suffix)
    {
    return function(x) { return prefix + x + suffix; };
    } 
    function censor(x)
    {
    x.innerHTML = censored;
    }
    switch (location.pathname)
    {
    case '/':
    case '/index.php':
        foreach(document,
            enclose('id("punindex")//td[@class="tcr" and span/@class="byuser" and (', ')]'),
            enclose('span="by ', '"'),
            censor);
    break;
    case '/viewforum.php':
        var vf = document.getElementById('vf');
        var nodes = getNodes(blocked,
                 vf, 
                 enclose('.//tr[td/@class="tcl"][', ']'),
                 enclose('.//a/@href="viewtopic.php?id=','"'));
        for (var i = 0; i < nodes.snapshotLength; ++ i) 
        {
            var node = nodes.snapshotItem(i);
            node.parentNode.removeChild(node);
        }
        var nbsp = String.fromCharCode(160);
        foreach(vf,
            enclose('.//td[@class="tcr" and span/@class="byuser" and (', ')]'),
            enclose('span="by' + nbsp, '"'),
            censor);
        foreach(vf,
            enclose('.//tr[td/@class="tcl" and td//span/@class="byuser" and (', ')]'),
            enclose('td//span="by' + nbsp , '"'),
            function(x)
            {
            var id = document.evaluate('.//div/a[1]/@href',
                           x,
                           null,
                           XPathResult.FIRST_ORDERED_NODE_TYPE,
                           null).singleNodeValue.value;
            id = /\d+$/.exec(id)[0];
            blocked.push(id);
            GM_setValue('blocked', blocked.toSource());
            x.parentNode.removeChild(x);
            });
        break;
    case '/viewtopic.php':
        var punviewtopic = document.getElementById('punviewtopic');
        function isBlocked()
        {
        if (blocked.length > 0
            &&
            new RegExp('[?&]id=(' + blocked.join('|') + ')(&|$)')
            .test(location.search)) return true;
        var pagelink = document.evaluate('.//p[@class="pagelink conl"]',
                         punviewtopic,
                         null,
                         XPathResult.FIRST_ORDERED_NODE_TYPE,
                         null).singleNodeValue;
        if (blocked.length > 0
            &&
            getNodes(blocked,
                 pagelink,
                 enclose('a[1][', ']'),
                 enclose('starts-with(@href,"viewtopic.php?id=','&p=")')).snapshotLength > 0) return true;
        if (document.evaluate('count(a)',
                      pagelink,
                      null,
                      XPathResult.NUMBER_TYPE,
                      null).numberValue > 0) return false;
        var starter = document.evaluate('.//div["blockpost rowodd firstpost"]//div[@class="postleft"]//strong[1]//text()',
                        punviewtopic,
                        null,
                        XPathResult.STRING_TYPE,
                        null).stringValue;
        for (var i = 0; i < banned.length; ++ i)
            {
            if (starter === banned[i]) return true;
            }
        return false;
        }
        if (isBlocked())
        {
            document.title = 'Censored'; 
            document.body.innerHTML = '<div style="text-align:center;margin-top:20pt;font-size:20pt;color:red;">Censored</div>';
            setTimeout('history.back()', 1000);
            break;
        }
        foreach(punviewtopic,
            enclose('.//div[@class="postleft"]/dl[', ']'),
            enclose('.//strong[1]//text()="', '"'),
            function(x)
            {
            x.innerHTML = censored;
            x.parentNode.nextSibling.nextSibling.innerHTML = censored;
            });
        foreach(punviewtopic,
            enclose('.//blockquote/div[@class="incqbox" and (', ')]'),
            enclose('h4="', ' による投稿:"'),
            censor);
        break;
    }
})();