After reading through NIP 23 ..it kinda makes sense ..

Format

The content of these events should be a string text in Markdown syntax. To maximize compatibility and readability between different clients and devices, any client that is creating long form notes:

MUST NOT hard line-break paragraphs of text, such as arbitrary line breaks at 80 column boundaries.

MUST NOT support adding HTML to Markdown.

But why remove this from NIP 01 ? Is it too much performance tax ?