You are correct that they do not come right out and say that in the faq. I'm not sure if they did in the past.
However in the FAQ at:
https://slashdot.org/faq
At section Subscriptions with question:
Why subscribe to Slashdot? Can't I read for free?
You find the link:
https://slashdot.org/faq#subsc...
That takes you further down the page with more details where as you said it does not mention this.
*It is an unmentioned plum.*
While you are logged into your account observe on the upper right where I expect you have your Slashbox.
If you don't then go enable it.
With that enabled you have the default content that goes in your Slashbox and it lists your current Karma.
Mine has been Bad since I think about 2007. Haven't seen a mod point sense.
Below Karma you have three links:
Journal Subscription Account
Subscription is this link:
https://slashdot.org/subscribe...
Where in you read:
Absolutely nothing about this!?
Hrm. I could have sworn I read about this and didn't just figure it out on my own.
Okay they either covered this before and removed it. Not sure and don't know why they would do that.
Or I read this in a post several years ago and just assumed everyone I've been reading complain about this just didn't want to subscribe.
I subscribed a few years ago and wanted encryption and also had trouble with this feature due to redirects.
I resolved this by putting
*slashdot.org*
in my forced HTTPS NoScript settings and then added
slashdot.org/my/login
into the whitelist for the never force https list.
Anytime my session/cookie expires I put in slashdot.org/my/login and then get redirected to a https slashdot url.
Hope that helps you and many others and that they don't degrade this for some reason!?