On the torrent search page, you'll see your username at the upper left. Click on that to get a drop-down menu. From that menu, click on "Details & Stats." On that page, towards the bottom, you'll see "Torrent comments" with a number to the right. Click on that number and it will bring you to a page with all your comments, 25 per page, overflowing onto additional pages.
I think this will only show comments on torrents that are still active (posted) in the system, even if it's dead with no seeders. If you commented on a torrent that was taken down for one reason or another, I don't think that will show up. (I'm not absolutely sure about this, but I did a small random sample of my older comments, and every torrent showed up.)
Happy hunting!
