I have a Forum set to Threaded layout. I need to post a topic for discussion (e.g. how long do you boil an egg) and gather responses by replies to this question. BUT, I want nesting only 1 reply deep i.e. NO replies/comments to the replies (2 mins, 3 mins) - just a question and a bunch of untested replies with no comments. 
I tried setting Threaded Layout - Replies Nesting Levels Deep = 0 as per screenshot and cleared every cache in site (wpForo and site - which I've actually uninstalled), hard-refresh on the site and ... I can still post replies to replies.... 

Am I missing something?