taskmanager.user.js

// ==UserScript==
// @name        Insert <del></del> as pressing Ctrl+D
// @namespace   http://lowreal.net/
// @include     https://*.g.hatena.ne.jp/*
// ==/UserScript==

location.href = "javascript:"+encodeURIComponent(uneval(function () {
	document.body.addEventListener("keydown", function (e) {
		var target = e.target;
		if (target.nodeName.toLowerCase() != "textarea") return;
		if (e.ctrlKey && e.keyCode == 68) {
			try {
			e.stopPropagation();
			e.preventDefault();

			var cursor    = target.selectionStart;
			var value     = target.value;
			var lineStart = value.lastIndexOf("\n", cursor);
			var lineEnd   = value.indexOf("\n", cursor);
			lineStart = lineStart == -1 ? 0 : lineStart;
			lineEnd   = lineEnd   == -1 ? value.length : lineEnd;
			var replace   = value.substring(lineStart, lineEnd);
			replace = replace.replace(/([-+]* *)(.+)/m, '$1<del>$2</del>');

			target.value = value.substring(0, lineStart) + replace + value.substring(lineEnd);
			target.selectionStart = cursor + 5;
			target.selectionEnd   = cursor + 5;

			} catch (e) { alert(e) }
		}
	}, true);
}))+"()";