Since all I did was change the name of two forums, there’s no way it could have unsubscribed you from anything.
Then some other glitch happened at about the same time. I only keep subscriptions to threads I have commented on, and I go through every few months and unsubscribe to the oldest stuff that has gone inactive or that I no longer have interest in. So I probably had between 5 and 10 subscribed threads since the last time I did that. But when I realized I was only getting email notifications for one thread, even though there should have been others, I checked my list and there was only that one thread subscribed. I went ahead and unsubscribed from that one, since I was not reading it anymore, but I have no idea what happened to the rest that should have still been on my list.
Edit: and I just went now to look and make sure this thread was showing as subscribed, and there are 24 other threads showing now that were not when I made my other post. Some of the ones showing again are ones I was sure I had manually unsubscribed to, so something weird is going on.