Markdown gives most people >95% of the formatting they want to do.

It's easy and fairly intuitive to write (most of it, anyway).

It's easy to read in different formats and ways (HTML, plain text).

It doesn't add highly complex rendering issues. I've worked on two email clients in the last ten years, and the amount of weird HTML some send is just bonkers. Is <div style="position:fixed"> in emails crazy? Yes. Do you need to deal with it? Also yes.

The point is: markdown is HTML, not something else.

It's not. Markdown is markdown. It can render to HTML, but that's a different thing. I struggle to understand why this is even a point of contention.

Since it supports any HTML tag, it is irrelevant.

Mandate markdown and MTAs and marketing departments will send you markdown only made of pure HTML.

That's quite the pivot from "markdown is HTML". But no, it probably shouldn't support HTML tags, or support it with limits. And maybe also a few other things like #-headers also shouldn't be supported as it can be too easily to do by accident. All of that seems pretty obvious in all but the most aggressively pedantic reading.

Is C amd64 assembly then?

If your C code end up like that, yes:

``` #include <stdio.h>

int main() { /* my software in ASM */ __asm__ ( [...<insert your assembly code lines here>...] );

    return 0 ;

} ```

And you are pretty sure this is pretty much what would happen with markdown in emails if it ended up being mandatory. You would end up with emails entirely made of html.

Not in the slightest.

You can’t make elaborate layouts with Markdown. You can’t obfuscate text in images or make hidden links or inject JavaScript.

Just some basic text styling (headers, italics, bold type), and images. Everything necessary to make a well-formatted message — which is what email is supposed to be — instead of mailing a web page, in a medium that hasn’t been refined for quality and safety like modern HTML+CSS has.

If emails could be marked up with the subset of HTML that Markdown is able to generate without having inlined HTML tags, email markup would be so pleasant. Just bold/italics, some headings, tables, properly flowing text, code blocks, horizontal rule, links, and images.

you just need gemtext. Bold/Italics can be done with unicode, no need for a markup language.

Images can just be links and it would be a setting on the client to open it or not. Like what the Lagrange gemini browser does: it lets you click on a link to an image to load it.

I would argue that even tables are superfluous, you could put a csv file in a block quote and people's clients could just render it optionnally.

Yes, this. Many more would be fine with HTML email if it didn’t work like IE6—and honestly, the only reason it does is because of decades-old enshittification that we failed to address at the time.