Hi, the phppp forum use a non-standard element "mwthree" to useless feature, but it prevent Safari user to view messages. After first layout, the messages was hidden by a sort of second layout. The W3C says " a user agent encounters an element it does not recognize, it must process the element's content" but it did not specify the way to evaluate this unknown element.
Created attachment 20389 [details] reduction The problem is not an unknown tag but rather the "mw3.js" script used in the forum. I have added a test reduction. Safari and Opera show identical results, I don't know if that's a bug or not. The script actually uses a workaround that tests for Opera but not for Safari. As a quick fix you might try the following: in mw3.js line 113 comment out the code that tests for window.opera like this: if ( // window.opera && That makes it work with Safari, at least for me.
All browsers (Chrome Canary 106, Firefox Nightly 105 and Safari 15.6 on macOS 12.5) render the reduction test case same and show two line of text. Since all browsers are in consensus, I am going to mark this bug as "RESOLVED CONFIGURATION CHANGED". If I am wrong or web-spec say differently, please reopen and mark accordingly. Thanks!