Having thought about it, I’m against this idea.
Markdown is already a rickety construction with different syntax options to produce the same effect and symbols with multiple possible effects. I feel that building on a house of cards makes it even more imperative for there to a strong and clear need for any divergence from “standard” markdown.
In Obsidian, we already have
[[ ]] wiki-links. But these have the advantage of much greater speed in use for a function that is key to Obsidian. And thus usage is shared with most apps in the PKM space. And there’s already an option to use markdown linking and a conversion to standard markdown gas been promised.
==highlights== An important function for editing and revising and making selected text stand out. It is not common in markdown, but some programs such as Typora use it.
#tags Not a standard feature, but some apps, such as Epsilon Notes, recognise it and it’s a key function for document management.
Obsidian is committed to be as interoperable as possible and the proposed @ syntax is very rarely used in markdown - the only example I’ve come across is the the Noteplan cited above (which is designed formeetingsetc and appears to be a database rather than using markdown files - and the actual functionality is identical to #. So I conclude that the size of the gain for most users doesn’t justify adding an extra item of syntax to markdown files.
Of course, plugin developers can do anything they want, and so long as it’s never incorporated into the main program it doesn’t bother me. If someone does a plugin for meetings, contacts etc, I can see that they might want to use it. Even so, I’d think it was better for the use to exist in something like a .json rather in the notes themselves.