Whenever viewing a comment thread in a separate window by picking "show thread", the site suddenly think you are logged out and therefore you can't reply to the comment. Basically it is impossible to reply to comments currently.

I thought it was just my login cookie having aged away or something but attempting to log in shows that you are already logged in. Refreshing the site doesn't help - you are still logged in when viewing the main Q&A but not when viewing comments.

Futhermore when viewing the comment thread and clicking "sign in", nothing happens. Probably because I'm actually already signed in.

Update: Replying to comments here on meta seems to be working just fine. It does not show me as signed out and the reply button is there. The comment thread that is not working at all is this one https://software.codidact.com/comments/thread/11940#comment-29615.

Also when I tried it just now I got sporadic error messages, something like "failed to open comment thread", but I cannot reproduce that again. It may be the specific comment thread that is broken perhaps?

Update 2: Refreshing the comment thread page several times until the Cloudflare thing pops up seems to bring the reply to comment eventually pop up and shows me as logged in. However, that doesn't work from the Q&A post where the option to directly reply to the comment without opening it in a separate window is still missing no matter how many times I refresh it.

Update 3: After finally being able to post a reply to the comment after doing the above refreshing, the comment thread now works again and I can see the "reply to this thread" button from the main Q&A once more.