Maybe libreoffice needs a more strict word online compatibility mode that compromises UI and functionality for as perfect as possible compatibility.

For instance a user in the thread mentioned all background colors can be applied in libreoffice, but in word online some are restricted.

Ux having those restricted colors grayed out by default with a hover note why seems perfect to keep compatibility and show where word online is wonky.

Hope this makes sense, will have to pay or in a better format to the issue tracker tomorrow.