w3m sets the column width for the HN nested table spacer all to one value, so you visually only get two levels on nesting. Here is a screenshot of this thread as rendered by w3m:

https://lh3.googleusercontent.com/rZ1yOj55fvQqtWWbOnoSTpvCgx...

w3m table rendering is based on a heuristic algorithm and fails in some cases. See the "Table rendering algorithm in w3m" section in:

http://w3m.sourceforge.net/STORY