Hi, try it after being logged-in (obviously), but with your ABP being disabled completely. And see if that works. There is nothing wrong with the site, and 'Write new Comment' works fine.
The problem is from your end, hard part is to determine what that is. ATM, I think it's the ABP software, or something similar that you may be using. Also, check if cookies are allowed on your browser, or if something similar is blocking 3rd party cookies. I personally believe one of the above methods would work. If it is ABP, you'll have to put some source code to be exempt from being blocked by ABP in the filter list, and not just the site name, especially if the rest of the site works fine. We'll worry about that later. Firstly allow all cookies on OS, if that doesn't work, disable ABP and see if that works.
'about:blank#blocked' I don't get that, no matter what I do. Right clicking would never work for "Write new comment", but at the very end, try also changing your server location, if a VPN used. I doubt that has anything to do with it, just the word
"blocked" concerns me.
Good luck.
Edit: I see after I was constructing my essay, Func got there before me.
If filtering the link under "Write new Comment" is needed, Func is the best man for the job. He's good at finding the source code for the ABP filter list