Every other version of phpBB I've used will allow me to autosubscribe to threads I have posted in (or created), and I do not see that option here.

Doing a little digging (as far as I can being just a user), I'm not seeing the option to configure that; though I do get notified for replies to topics I've posted in, so it must be the default (and only) behavior.

Yeah, not working for me for some reason... I had to go back to every thread I've posted in and manually subscribe.

But then again, it takes me fifteen minutes of trial-and-error just to get logged into the forums anyway--dunno if it's Firefox, it's containers, my username/account or some combination, but it's frustrating a all get-out.