What I had was nested inside an Ordered List and bracketed content just did not appear. It is working now in Firefox-esr, vimb (webkitgtk-4.0) and ungoogled-chromium.
www/ungoogled-chromium has had a number of patches/updates and I cannot recall what browser I was using when I had the issue. I did double check the formatting, removed it and regenerated a second time with the issue persisting prior to reporting the issue. At that time I did not try different rendering engines.