自分のIDやページのURLがDashboardなどから取得できない時でも部分的に動作するように修正した。また、Likeなどのページでも動作するように変更した。

a_smart_dashboard_have_my_id.user.js

// ==UserScript==
// @id             A smart dashboard have my id
// @name           A smart dashboard have my id
// @namespace      http://mitukiii.jp/
// @author         mitukiii
// @version        0.0.3
// @update         2012-02-16T03:26:28.351Z(GMT+09:00)
// @description    TumblrのDashboardで自分からReblogされた/自分のidを含んだpostを折り畳むスクリプト
// @include        http://www.tumblr.com/dashboard*
// @include        http://www.tumblr.com/show/*
// @include        http://www.tumblr.com/likes*
// @include        http://www.tumblr.com/liked/by/*
// @include        http://www.tumblr.com/tagged/*
// @exclude        http://www.tumblr.com/dashboard/iframe*
// @run-at         document-end
// @priority       0
// @compatibility  Firefox 10.0(Scriptish 0.1.7), Chrome 17.0.963.46, Safari 5.1.2(NinjaKit 0.8.5), Opera 11.61 on Windows 7 Home Premium SP1 64bit
// @charset        UTF-8
// ==/UserScript==

/*jslint browser: true, maxerr: 50, maxlen: 80, indent: 4*/
// Edition 2012-02-14

(function executeAddStyleAndEventListener(doc) {
    'use strict';

    var posts, containsMyPageUrlElm, hiddenInput, myPageUrl, myId,
        containsMyIdXpathExp, xpathExp, addClassName;

    posts = doc.getElementById('posts');

    if (!posts) {
        return;
    }

    containsMyPageUrlElm = doc.querySelector(
        '#post_controls_avatar, .is_mine .post_avatar:only-child'
    );
    hiddenInput = doc.querySelector('[name="t"]');

    if (containsMyPageUrlElm && hiddenInput) {
        myPageUrl = containsMyPageUrlElm.href;
        myId = hiddenInput.value;

        if (!(myPageUrl && myId)) {
            return;
        }

        containsMyIdXpathExp = [
            ' or ',
            'div[contains(concat(" ", @class, " "), " post_content ")]',
            '//*[',
            'self::td[contains(concat(" ", @class, " "), " quote_source ")]',
            ' or ',
            'self::p',
            ']/',
            'a[',
            'starts-with(@href, "' + myPageUrl + '") and ',
            'not(@class) and . = "' + myId,
            '"][',
            'following-sibling::text()[1][. = ":"] or ',
            '(',
            'preceding-sibling::text()[1][contains(., " (via ")] and ',
            'following-sibling::text()[1][starts-with(., ")")]',
            ')',
            ']'
        ].join('');
    } else {
        containsMyIdXpathExp = '';
    }

    doc.head.appendChild(doc.createElement('style')).textContent = [
        '.is_mine:not(.new_post),',
        '.related_me {',
        '  opacity: 0.5 !important;',
        '  max-height: 1em !important;',
        '  overflow: hidden !important;',
        '}',
        '.is_mine:not(.new_post) > .post_content,',
        '.related_me > .post_content {',
        '  display: none !important;',
        '}'
    ].join('\n');

    xpathExp = [
        'descendant-or-self::li[',
        '(',
        'contains(concat(" ", @class, " "), " not_mine ") and ',
        'contains(concat(" ", @class, " "), " is_reblog ") and ',
        '(',
        'div[contains(concat(" ", @class, " "), " post_info ")]',
        '/',
        'a[count(../a) = 1]',
        containsMyIdXpathExp,
        ')',
        ') or ',
        '(',
        '(',
        'div[contains(concat(" ", @class, " "), " post_controls ")]',
        '/',
        'form[@action = "/delete"]',
        ') and ',
        '(',
        'div[contains(concat(" ", @class, " "), " avatar_and_i ")]',
        '/',
        '*[last()][contains(concat(" ", @class, " "), " post_avatar ")]',
        ')',
        ')',
        ']'
    ].join('');

    addClassName = function addClassName(target) {
        var contextNode, containsMyIdPost, containsMyIdPosts,
            containsMyIdPostsLen;

        contextNode = target.target || target;

        if (contextNode.tagName === 'LI') {
            containsMyIdPost = doc.evaluate(
                xpathExp,
                contextNode,
                null,
                9,
                null
            ).singleNodeValue;

            if (!containsMyIdPost) {
                return;
            }

            containsMyIdPost.classList.add('related_me');
        } else if (contextNode === posts) {
            containsMyIdPosts = doc.evaluate(
                xpathExp,
                contextNode,
                null,
                7,
                null
            );
            containsMyIdPostsLen = containsMyIdPosts.snapshotLength;

            while (containsMyIdPostsLen) {
                containsMyIdPosts.snapshotItem(
                    containsMyIdPostsLen -= 1
                ).classList.add(
                    'related_me'
                );
            }
        }
    };

    addClassName(posts);

    posts.addEventListener('DOMNodeInserted', addClassName);
}(document));