I could never understand why people favour Markdown over HTML. Markdown is the worst idea when it comes to storing data. It's not standardised so there are dozens of incompatible flavours and incompatible Markdown -> HTML and HTML -> Markdown converters. Introducing Markdown to your app will eventually bring troubles but developers rarely notice this cause all seems to work initially when they test the simplest cases.
So, why did we create a Markdown data processor for CKEditor 5? (You can find a demo of it here: https://docs.ckeditor.com/ckeditor5/latest/features/markdown...) It was just to showcase that you can actually do that. But I'd never recommend it to anyone. HTML as a format is standardised and stable and there are even more tools to process it.
PS. There's the CommonMark standard, but it was created too late and its adoption is low.
