If you've posted on a tactic forum you automatically track (follow) it. If anyone else then posts on there you should receive an alert on your homepage.
If you want to go back over a tactic, you can review your most recent 25 on this page
http://www.chess.com/tactics/myhome.html
After completing a tactic, if you have settings on 'stop after each one', look under the tactic board you'll see there it shows 'Comments'.
How do you go back to a Tactics Trainer problem to review and to see any comments?
Thanks,
Greg