Yes, I fully understand that.

The point is that if so some reason, I'm not logged in, and I go directly to a thread, I can't respond to that thread unless I go to the main page, log in and then have to go back to that thread.

Pretty much all aother forums I visit (many different technologies) have a mini login area on the top of each thread page, or a log in button. Then, after log in you are still on the thread that you directly went to and the log in button is changed to log out.

It is a nice user friendly thing to have on each page.

This is the site suggestion thread, afterall :D