A few people have had difficulty blocking users, including @markedman5 and @docduany.
While I'm still unsure why this is happening, I think this workaround will resolve the issue. First, hit the link:
https://brewerfanatic.com/ignore/
Use the autofill at the top of the page to find the correct user you want to block. You need to select their name from the drop-down so the system knows precisely who you want to block.
Then make sure you check all the boxes below: posts, messages, replies, etc.
Then hit update preferences or whatever it says and that should activate the ignore.