ExtendScript: control font settings of substrings within a layer

Heyo!
I'm trying to automate the creation of the same comp but with different text and fonts

Some layers have text different font styles (e.g. "Hello world!").

I would like to be able to insert text (e.g. "Goodmorning planet!") and specify what style each word has (ideally, "Goodmorning planet!")

But by changing the text of the TextDocument object, it defaults all the text to a single font style (the one of the first character).

Is there a way to specify character-per-character which font to use?

Maybe there is an option that allows AE to read text as it was Markdown (e.g. **this text is bold** = this text is bold)

Thank you for the help!