For me, the less compatible Discourse is with regular markdown, the harder some other things would become, like moving content between Discourse and other things that use markdown. (My sites and documentation generally use markdown or MDX.)
If some kind of feature like this gets added, an alternate idea for implementation would be to use a system similar to Confluence or Notion where the / (slash) character opens up a menu.
Here’s Confluence:
Here’s Notion:
If a similar feature were in Discourse, a slash could open up a menu which would include “Link” as an option. If “Link” is selected, then the user could do a search for other posts and a normal markdown link would be inserted in the editor.
I’m not requesting the feature but am just mentioning an alternate idea for implementation that wouldn’t make the raw content diverge further from regular markdown. 