Some users (incl. me) on Czech Wikipedia confirmed that it wasn't possible to insert characters from Edittools. When editing, clicking on any character (groups) but non-breaking space does nothing. Clicking on nbsp does insert it but the browser console reports: Use of "insertTags" is deprecated. Use mw.toolbar.insertTags instead.

This could be Regression introduced by rECHIb2f7c4c507e5.