How about the option to automatically subscribe to threads I post in - so I get an email if there is a new post in that thread? [But not an email for every single new post - just one email to let me know there has been activity in the thread since my last visit to the site.]

Can't have that, not in the General Forum at least. If posters had that facility there might be more interesting threads than the interminable lists and word association stuff.

how about a "tracker" option. When some poster posts that you have an interest in reading, then the tracker message lets you know or links you to it.

if you haven't opted to follow, then it goes as usual. no message, no link.