This is an awkward question, combined with a irritated observation. Please forgive the irritated tone.
I am very frustrated by the repeated messages I get on YouTube if I want to do as little as click the thumbs-up icon on a comment. Immediately a message pops up, saying to "Sign-in again to post a comment!"... I'm already fully signed in and have access to my account, while the commenting seems to be forcing me a double sign-in.
First of all, I don't really understand what system could be setup that would require a second sign-in, except for obvious cases of security like major e-commerce sites such as amazon and ebay, where an account session may be active for a long time using cookies to add items to a cart, or similar low-level security actions (ie tracking my own product-view history for product recommendations). Those, separate from high-level security actions that ought to require authentication at the moment of the action, like purchasing or changing password (which is in virtually every user-account system across the web).
What would be the best way for this double-sign-in to be simplified? And truly, what is the actual meaning for it. It's a horrendous user experience IMHO, and has nothing to do with high-level security for payments or account management.
It makes me confused, and leads me to wonder, am I'm missing something in my observation of this particular system?