Just posting in a thread should get you notifications when there are posts in it, or you can goto the top of the page within the thread and click on "Thread Tools" and subscribe. If you are not getting notifications, you can change those settings in your profile. It is in forums actions, general settings and there is a drop down for "
Default Thread Subscription Mode:"
Change that to instantly, and it will sub you to threads to comment in
Thread jacking is just posting off topic content in someone else's thread, some people get bothered by it. Myself not only do I expect it on a marijuana forum where staying on topic is not the norm, I enjoy seeing where things go