• IE and EdgeHTML never supported <details>, so until comparatively recently you had to polyfill it. Now, you need not worry about this, because you should actively not support IE or old Edge.
• WebKit still doesn’t use ::marker on summary. If you’re hiding the disclosure marker, you can’t just use `summary { display: block }` or `summary::marker { display: none; }`, and must remember to `::-webkit-details-marker { display: none }` as well. And if you want to change it, you can’t just change its list-style-type or manipulate ::marker, but must clobber the whole thing and use ::before or similar.
(Aside: if you don’t use a Mac, Epiphany is a good WebKit-based alternative to Safari on other platforms that will exhibit most of the same behaviours and quirks as Safari.)
• WebKit still doesn’t use ::marker on summary. If you’re hiding the disclosure marker, you can’t just use `summary { display: block }` or `summary::marker { display: none; }`, and must remember to `::-webkit-details-marker { display: none }` as well. And if you want to change it, you can’t just change its list-style-type or manipulate ::marker, but must clobber the whole thing and use ::before or similar.
(Aside: if you don’t use a Mac, Epiphany is a good WebKit-based alternative to Safari on other platforms that will exhibit most of the same behaviours and quirks as Safari.)
Other than that, it’s all pretty solid now.