In some other boards I participate in, there is an option to automatically subscribe to a topic that you either start or respond to, and to get email notification of further replies. I can't find that option here. Does it exist?

Yes it does - you can access it from the options dropdown at the top of the page for each thread.

Thanks Andrew. I'll use that feature. Is there a way to automatically subscribe, rather than doing it one thread at a time?

Not that I am aware of ...