Clicking the binos on a thread does not add it to my watchlist. What I've done to work around it the past few years is post a reply with just a thumbs up/down emoticon to make sure its added to my topics responded to, because adding a thread to your watchlist most of the time doesn't work. Sometimes when I click the watchlist after adding a thread I haven't replied to, I'll see it there, but fairly quickly it will disappear from the "topics I am watching" list.
It says: "(topics automatically purged after 10 days of no replies.)" but this thread hasn't been responded to since 2012.

To reproduce: use account with watchlist privileges to add threads to "topics I am watching" by clicking the binos. Access the watchlist and see them there, then look back after a few days as they disappear. Do this on old threads as well, and post a reply.
I really can't put my thumb on what is going on here. I've searched out old threads I've started and added them to my watchlist and they show up at first and drop off before 10 days even when I make a reply to them. Is this an indexing thing?
It says: "(topics automatically purged after 10 days of no replies.)" but this thread hasn't been responded to since 2012.

To reproduce: use account with watchlist privileges to add threads to "topics I am watching" by clicking the binos. Access the watchlist and see them there, then look back after a few days as they disappear. Do this on old threads as well, and post a reply.
I really can't put my thumb on what is going on here. I've searched out old threads I've started and added them to my watchlist and they show up at first and drop off before 10 days even when I make a reply to them. Is this an indexing thing?