If you go to the matches "home page" where it shows who is facing who for the particular match you will see a bunch of comments at the bottom. Scroll to the very end of the comments and you should see the following type of box. Make sure it is unchecked. 
If this doesn't work send me a link to the match and will try something else.
Thanks, Gytrash, but the problem is that once I unregistered from the match the "tracking turned off" box disappeared, just like the box where I would enter a new comment disappeared. I didn't expect that I would still be able to enter comments, but I don't see why I also lose my ability to untrack.
Here's all I get now at the bottom of the column of comments:
It goes straight from the last comment to the standard links at the bottom of the page.
Here's the match URL:
I see what you mean. Did you try going into your group menu and change the alerts or the forum settings for your team? The only thing is I don't think you can choose exactly which ones to not recieve updates from. Like if there are four team matches you can't pick which ones to recieve updates from or not receive from. Maybe the chess.com staff have an idea or solution to remedy this issue.
I was registered for a team match and unregistered when it became clear it was not going to start for several more weeks. I'm still getting comment alerts for the match forum, but I no longer have the ability to comment in or untrack from the forum. Anyone know how I can stop receiving alerts for new comments in that match?