[Isomorphic]

In today's 13.0 build.

[Hirn]

Unfortunately after being added to the code

textEditor.setStyleWithCSS(true);

stopped working

textEditor.setValue("<b>text1</b> text2");

[Isomorphic]

Did you try setUseDesignMode(false)?

[Hirn]

Now everything is working.
Thank you very much.

[Hirn]

For complete happiness, there is still the option to choose the font size in PX. If you don't mind, I'll try to outline a couple of solutions for this case.