I just posted a reply to "Are there problems on the site?" The thread list for Feedback & Technical Support shows it as subscribed (green checkmark):



However, when I go to my Subscriptions page even 20 minutes later, it isn't showing up there:



Thread Tools also shows me as subscribed and offers me the option to unsubscribe.

Epilogue:
I finally did unsubscribe, then resubscribe, and now the thread is showing up in Subscriptions.