I'm broadly in favor, but with an edge-case caveat. I use Markdown almost exclusively these days, and use the @name convention there. But the one time I *cannot* use Markdown is because of this feature: when I'm linking to a Medium URL (which often has an @ *in the URL*), this causes the link to break.

So there needs to be some sort of way to escape out of this -- to signal, "no, this @ isn't trying to link to a user".