Am I missing an obvious option on the preferences page as I can't see an option to just receive alerts about the thread starter posting in a thread rather than everyone who replies?
Short of it is unless someone is individually willing to put up $35 bucks for it (if you are PM me and I'll create an option in Account Upgrades for you to do so, and even throw in a special banner) then it will show up based on site revenue and other needs.
But the addon is on the list, just no real clue when it will get purchased.