This is QUITE RIDICULOUS, when a product is in it's next iteration, you shouldn't feel that you are taking 1 step backward.
Think about this for a second:
Not being able to do this BASIC TASK on a page is both ...
Same Problem here. The SharePoint 2013 Update July 2019 solved the problem for us.
It contains an updated SP.UI.Rte.js (06/12/2019).
PS: The classic editor parts of SharePoint 2019 has the ZWSP bug too. The modern pages editor part has no ZWSP problem.
We replaced the SP.UI.Rte.js and SP.UI.Rte.debug.js of SharePoint 2019 with the versions of the ...