The W3C documentation suggests it cannot be done:
Note that comments are markup.
This basically means that a <!-- ...> comment tag is just like any other tag, so <a <!--title="need to be comment out"-->>a link</a> is as wrong as <a <span></span>>a link</a>.
For quick hacking I believe a common option is to rename that attribute. While you obtain invalid HTML, you can temporarily remove the attribute:
<a xtitle="need to be comment out">a link</a>
If you happen to be using a server-side language, you can also use its own comment syntax. For instance, in PHP you can do this:
<a <?php/*title="need to be comment out"*/?>>a link</a>
… which generates this HTML:
<a >a link</a>
… and in ASP.NET you can use <%-- Comment goes here --%> while the ASP.NET MVC Razor syntax is @* Comment goes here *@.