Normal forum behaviour is to send one alert when a new post is made, then nothing more until the subscriber visits the thread and catches up to the last page. Very handy to keep inbox pollution down with busy threads. The message sent by the forum software indicates this is the intention here, but I have been getting individual alerts for each post in the skip Kickstarter thread regardless. That is the only busy thread I've subscribed to so far so no idea if it is just with the private forum or something.
My PEP Badge Tracker: An easier way to track your PEP Badge Progress