Not to mention that thread title with new post is BOLDED, (so if you read an trhead it is unbolded - and if you return in some time and someone added a post - it is bolded again)
at the same time you can check if someone replied to your post - you can see if the last submitter is you or someone else
And as this would not be enough you can pick some threads as your favorite - also you can be informed by email that new post is added. (in settins when you have already picked favourite threads)