Wikifreedia is better for looking at one page at a time, on a wide screen, but not so great on cell-phones screens, or when you want to look at multiple pages simultaneously.
The Asciidoc site, itself, displays the sidebars in the center, as they're using frames or something. Looks fine. Still gives it more emphasis, with the formatting.
https://docs.asciidoctor.org/asciidoc/latest/blocks/sidebars/#delimited-sidebar-syntax