let us see and use the symbols ( sad faces and happy faces)
Wenjun Gong (MSFT Product Team) commented
Thanks for posting this idea.
To insert symbols, you can go to the "Insert" tab on the ribbon then click the "Symbol" button. So far there are only limited symbols there. The happy face symbol is in the list while sad face is not. But you should be able to copy the symbol from another place (such as a website or another document) then paste into Word online. And we will plan to add more symbols in the future.
Hope this helps and please keep on the posting!