Really?
There’s an FAQ titled “How do I subscribe to specific forums or topics?”, and then some inaccurate instructions that don’t work detailing how to do so.
This would suggest that you’re meant to be able to, but it just so happens that the instructions are wrong and/or out of date.
Surely that FAQ should be removed to avoid confusion if it really isn’t possible. But more to the point, why on Earth can’t I get email notifications about responses? Having to poll the Sublime Forum to check for answers to my questions in this age of ubiquitous email notifications is ridiculous.