I Tested this and i can not literally reproduce this error.
I Opened your posts as signed in user , and i can both comment/read comments.
as anonymous (aka NON logged in user) i can READ comments but i can NOT comment, which is O.K. since in order to comment you need to login...
This is what i see as a non logged in user:
https://gyazo.com/d22bd5dca39fa8f8ac7d90cdd4d198e2
do you still see the server error?